The Chess Variant Pages




Seachess

By Christopher Hodde

Pieces; Starting Position; Notation

Words like "checkmate" etc. correspond to their equivalents in Fide-chess as long as not defined other. FIDE-rules like "stalemate", "four time-repetition" etc. are used if nothing else is said in this rules. Seachess is played on a chessboard-like board of 8x10 fields with two smaller rectangles of 2x8 fields on the longer sides which are called "haven".


        +---+---+---+---+---+---+---+---+
        | x | x | x | x | x | x | x | x |<--haven
        +---+---+---+---+---+---+---+---+
        | x | x | x | x | x | x | x | x |<--haven
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
        | x | x | x | x | x | x | x | x |<--haven
        +---+---+---+---+---+---+---+---+
        | x | x | x | x | x | x | x | x |<--haven
        +---+---+---+---+---+---+---+---+

The aim of the game is to checkmate the opponent’s commando-ship.


PIECES

The pieces are the following :

The Boat (B):

Boats move and capture like pawns in FIDE-chess but have the possibility to move two, three our four steps on their first move. En passant capture is only possible on the third rank. When a Boat reaches the last rank, it promotes to any piece other than a commando ship or a boat. If a boat cannot move forward but does not stand on the last rank (This is fact on a10;b10;i10;j10 for white and on a3;b3;i3;j3 for black), it will be able to do single non capturing sideway-steps until it is able to move forward again. Using a sideway step, the boat has to be moved in direction of the center board.

mo: move only
 c: capture

         +---+---+---+
         |   |   |   |
         +---+---+---+
         | c |   |   |
 +---+---+---+---+---+
 |   | B | mo|   |   |
 +---+---+---+---+---+
 |   |   |   |   |   |
 +---+---+---+---+---+
 |   |   |   |   |   |
 +---+---+---+---+---+
 | c | mo| c |   |   |
 +---+---+---+---+---+
 |   | B |   |   |   |
 +---+---+---+---+---+
 |   |   |   |   |   |
 +---+---+---+---+---+
 |   |   |   | mo|   |
 +---+---+---+---+---+
 |   |   | c | mo| c |
 +---+---+---+---+---+
         |   | B |   |
         +---+---+---+
         |   |   |   |
         +---+---+---+
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The Cruiser (C):

Cruisers move and capture like rooks in FIDE-chess but have the additional power to plant mines.
Planting a mine is a hidden move. The mine is activated immediately. This mine does now capture any piece that moves on the mined field - even if this piece captures the cruiser which has just planted the mine - (colour does not matter) and is removed together with the captured piece. Moving over a mined field is not possible.

After planting a mine, the cruiser cannot plant a second mine by the time it has moved to a field in its own haven to reload.

Mi: mined field
 m: move and capture


 +---+---+---+---+---+---+
 |   |   | m |   |   |   |
 +---+---+---+---+---+---+
 |   |   | m |   |   |   |
 +---+---+---+---+---+---+
 | m | m | m | C | Mi|   |
 +---+---+---+---+---+---+
 |   |   | m |   |   |   |
 +---+---+---+---+---+---+
 |   |   | m |   |   |   |
 +---+---+---+---+---+---+

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The Torpedo boat (T):

Torpedo boats move and capture like rooks in FIDE-chess but have the additional power to launch torpedoes. (which counts as a move)

Torpedoes can only be launched in "forward" diagonally direction. „Forward" is defined as the direction the piece moved in its last turn. A torpedo captures from afar up to two fields in "forward" diagonally direction. After launching a torpedo, the torpedo boat cannot launch a second torpedo by the time it has moved to a field in its own haven to reload. One should use pieces with an unequivocal front side for torpedo boats.

The torpedo boat just moved from its starting position.

t: capture with torpedo

 +---+---+---+---+---+
 |   |   | m |   |   |
 +---+---+---+---+---+
 | t |   | m |   | t |
 +---+---+---+---+---+
 |   | t | m | t |   |
 +---+---+---+---+---+
 | m | m | T | m | m |
 +---+---+---+---+---+
 |   |   | m |   |   |
 +---+---+---+---+---+
 |   |   | m |   |   |
 +---+---+---+---+---+
 |   |   | m |<--haven
 +---+---+---+
 |   |   | m |<--haven
 +---+---+---+

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The Submarine (S):

Submarines move and capture as knights in FIDE-chess do but have the additional power to submerge and move invisible for a certain time. A submarine can remain invisible for half of the turns it has been visible but not longer than for four turns. To submerge, the submarine is removed from the board and the first invisible move is noted on a sheet of paper (hidden moves). The submarine becomes visible again on the beginning of the first turn after the last "invisible-turn" (This does not count as a move).

A submerged submarine (sS) can move on every field even if it is already occupied by a piece other than a destroyer or a mine. To capture it either moves on the field where its victim stands and emerges on this field or it simply emerges and captures any piece other than a commando ship that stands directly "above" it. The remaining "underwater-moves" simply lapse. If a submarine gives check, this has to be announced and answered. If the check is answered the way, the submarine still gives check, the move has to be repeated.
A submerged submarine can only be captured by a destroyer or a mine.

F: piece

+---+---+---+---+---+---+---+---+---+---+---+---+
|   | m |   | m |   |   |   |   | m |   | m |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
| m |   |   |   | m |   |   | m |   |   |   |F m|<-- submerged Submarine can move "under" any piece
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   | S | Mi|   |   |   |   |   | sS|   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
| m |   |   |   | m |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   | m |   | m |   |   |   | m |   |   |   |D /|<-- Submarine cannot capture Destroyer or move under enemy Destroyer
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   | m |   | m |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
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The Destroyer (D):

Destroyers move and capture like bishops in FIDE-chess but have the additional power to force submarines to emerge. A destroyer forces every submerged submarine that stands on a field orthogonally connected to the destroyer’s field to emerge. If there is any piece other than a commando ship "above" the emerging submarine, it will be captured (colour does not matter).

The destroyer is the only movable piece able to capture a submerged submarine.

f: force submerged submarine to emerge

+---+---+---+---+---+
| m |   |   |   | m |
+---+---+---+---+---+
|   | m | f | m |   |
+---+---+---+---+---+
|   | f | D | f |   |
+---+---+---+---+---+
|   | m | f | m |   |
+---+---+---+---+---+
| m |   |   |   | m |
+---+---+---+---+---+

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The Aircraft carrier (A):

Aircraft carriers move and capture two field in any direction and are able to do a block able horse move. To define "block able", The horse move is defined as two steps in one direction and one step in a right angled direction. Aircraft carriers have the additional power to launch an aircraft (which counts as a move).

The aircraft (Aa) is able to capture an opposing piece on the outline of the square of which the corners are three fields diagonally away from the aircraft carrier. On its next move, the aircraft has either to move back to the aircraft carrier or to capture a second piece on the "outline". The aircraft can neither be blocked nor be captured.

The aircraft is able to capture as many pieces as it wants on one "flight" but while the aircraft is not on its aircraft carrier no other piece of the same colour can be moved.

a: capture with aircraft

 +---+---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   |   |
 +---+---+---+---+---+---+---+---+---+
 |   | a | a | a | a | a | a | a |   |
 +---+---+---+---+---+---+---+---+---+
 |   | a | m | m | m | m | m | a |   |
 +---+---+---+---+---+---+---+---+---+
 |   | a |   | m | m | m | m | a |   |
 +---+---+---+---+---+---+---+---+---+
 |   | a |   | F | A | m | m | a |   |
 +---+---+---+---+---+---+---+---+---+
 |   | a |   | m | m | m | m | a |   |
 +---+---+---+---+---+---+---+---+---+
 |   | a | m | m | m | m | m | a |   |
 +---+---+---+---+---+---+---+---+---+
 |   | a | a | a | a | a | a | a |   |
 +---+---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   |   |<--haven
 +---+---+---+---+---+---+---+---+---+

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The Commando ship (K):

Commando ships move and capture exactly as kings in FIDE-chess and have the possibility to castle either with the cruiser or with the torpedo boat. Check has to be answered.

The commando ship is not in check if there is a mined field between the attacking piece and the commando ship.
The player whose commando ship is checkmated loses the game.


+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
        |   |   |   | m | m | m |   |   |<--haven
        +---+---+---+---+---+---+---+---+
        | C |   | r | m | K | m | r | D |<--haven
        +---+---+---+---+---+---+---+---+

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STARTING POSITION

Starting position
for white:
  • 8 boats on c2,d2,e2,f2,g2,h2,i2,j2
  • 1 cruiser on c1
  • 1 torpedo boat on j1
  • 2 submarines on d1 & i1
  • 2 destroyers on e1 & h1
  • 1 aircraft carrier on f1
  • 1 commando ship on g1
The starting position for black is the mirrored position of white’s on the fields c11-j11 & c12-j12.

        +---+---+---+---+---+---+---+---+
        | c | s | d | a | k | d | s | t |<--haven
        +---+---+---+---+---+---+---+---+
        | b | b | b | b | b | b | b | b |<--haven
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
|   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+---+---+---+---+---+---+---+---+
        | B | B | B | B | B | B | B | B |<--haven
        +---+---+---+---+---+---+---+---+
        | C | S | D | A | K | D | S | T |<--haven
        +---+---+---+---+---+---+---+---+
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NOTATION

"In game notation" is necessary to be able to check whether all hidden moves have been legal.

  • B : Boat
  • C : Cruiser
  • M : Mine
  • T : Torpedo boat
  • S : Submarine
  • sS: submerged Submarine
  • D : Destroyer
  • A : Aircraft carrier
  • Aa: Aircraft
  • K : Commando ship (K because it is like a King and because I am from Germany)

Hidden moves have to be noted on an extra cheat of paper by the player who did the hidden move. The player doing a hidden move only notes his hidden move and informs his opponent about him doing a hidden move. After a player did a hidden move the according place in the notation is simply left out and is filled up later, according to the notes of the player. An (h) for "hidden move" is added. Doing a hidden move the player does not need to tell whether he plants a mine or moves his submerged submarine. cruiser; submarine

SPECIAL NOTATIONS :

planting a mine
Ce5 - M (h) Cruiser plants mine on e5 (hidden).
capturing by mine
Be4 - e5 - Mx Boat on e4 moves to e5 and mine captures.
submerging/emerging of submarine
Se4v - f6 (h) Submarine on e4 submerges and moves to f6 (hidden).
sSf6^x Submerged submarine on f6 emerges and captures.
forcing submerged submarine to emerge.
Da1 - e5 > f6^ x f6 Destroyer on a1 moves to e5 and forces piece on f6 to emerge which causes capturing on f6.
capturing with torpedo
Tj5 xt h7 Torpedo boat on j5 captures with torpedo on h7.
reloading
Ce5 - e2 < M Cruiser on e5 moves to e2 and reloads mine.
Tj5 - j2 < T Torpedo boat on e5 moves to e2 and reloads torpedo.
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COMMENTS

I have never played this game but I think I can guess a few things about the game.
I think the aircraft carrier is not as strong as it looks like because before the aircraft can start, you have to watch out whether the carrier cannot be captured in the next two moves. (The aircraft has to come back!) Rather than the aircraft carrier, I would think the Submarines to be the strongest pieces because they can move invisibly.

The board is twice as big as a normal chess board, although there are only 32 pieces. I have chosen this board because on an ocean, there are really long ways to go. Perhaps this could lead to a boring game.

You should really think twice about reloading torpedoes or mines in your haven because there will be long distances to go.

CREDITS