How do you play a battleship-style game?

Each side hides five ships on its own 10 x 10 grid: a carrier of 5 squares, a cruiser of 4, a frigate and a submarine of 3 each and a patrol boat of 2, 17 squares in all. Ships lie straight, across or down, may touch, and never overlap or leave the grid. The two sides then take turns firing at one square of the other grid, and each shot is called a hit or a miss. A ship sinks when every one of its squares has been hit, and the first side to sink all five ships wins. On this page you fire first, and a hit does not earn an extra shot.

Is this the Battleship board game?

No. Sea Battle is an original hidden-fleet grid game with its own name, grid, ship names and drawings. It is not the Battleship board game and is not affiliated with its publisher.

Does the computer cheat or see my ships?

No. The computer chooses every shot from what it has been told: the squares it has fired at, whether each was a hit or a miss, which of your ships it has sunk and the squares that ship covered, which the page shows you too for every ship you sink, and the lengths of the ships still afloat, which the rules make public. Its choice never reads the position of a ship it has not sunk; those squares are used only to call its shots hit, miss or sunk, the same way your shots are called against its fleet. On Easy it fires at random squares until it hits, then at the squares beside its hits, along the line once two hits touch. On Hard it counts every way the ships still afloat could lie among its hits and misses and fires where the most of those ways cross, favouring ways through hits it has not yet explained by a sinking. Neither level is perfect play.

Can ships touch each other?

Yes. Ships may sit side by side or end to end, but two ships never share a square, and every ship must fit inside columns A to J and rows 1 to 10. A placement that breaks either rule is refused with the squares at fault: with the carrier on B2 to F2, a frigate across from B2 is refused because B2, C2 and D2 are taken, and a cruiser down from H8 is refused because H11 is off the grid.

What happens if I fire at the same square twice?

The shot is ignored. Your shot count and hit count stay the same, it is still your turn, and a message says whether that square was a hit or a miss. The computer never fires at a square twice.

How do I place and turn the ships?

Pick a ship, then click or tap the square where it should start: it runs across to the right or down from there, and on a pointer or keyboard a preview shows where it will go. The Across or Down button, or R on the keyboard, turns the chosen ship, and a ship already on the grid turns in place when it fits. Placing a ship again moves it, Random placement lays out all five, and Clear takes them off. Start battle works once all five are on the grid. On a narrow screen the column and row pickers and the Place and Fire buttons are at least 44 pixels tall, so you never have to hit a small square.

Is my game saved, and can I undo a shot?

The game in progress, your ship layout and the computer level are saved in this browser after each change, when the browser allows storage, and come back when you return. A saved game that was edited outside the page, or damaged, is refused and a new game is set up. There is no undo once a shot is fired, because its result has already been seen. New game keeps your last layout on the grid so you can play again at once; once a shot has been fired in a battle, you press it twice to leave the game.

Can I play against a friend online?

No. This page plays one person against the computer on one device. There is no online matchmaking, no chat, and no betting or prizes, and your shots and ship positions are not sent anywhere.

Sea Battle

Sea Battle is an original hidden-fleet game for one player against the computer. Place a carrier, cruiser, frigate, submarine and patrol boat on a 10 x 10 grid by picking a start square and turning each ship across or down, or press Random placement; ships may touch but never overlap or leave the grid, and a refused placement names the squares that are taken or off the grid. Then you and the computer take turns, one shot each, and you fire first. Every square of the computer's waters stays blank until you fire at it, its remaining ships are shown only when the game ends, and the computer aims at Easy or Hard using only its own hits, misses and sinkings, never your hidden ships. A square you already fired at is ignored rather than counted, the turn log and the tally of hits and sunk ships update after every shot, and the game is saved in this browser when it allows storage. Both grids work with the arrow keys, and column and row pickers give a phone a full-size way to place and fire.

Computer level

Easy: it fires at random squares until it hits, then at the squares beside its hits, along the line once two hits touch.

your fleet0 of 5 placed

Your fleet: carrier not placed yet; cruiser not placed yet; frigate not placed yet; submarine not placed yet; patrol boat not placed yet.

carrier (5) goes across from the square you pick

Loading any saved game.

Ship to place

ships may touch, never overlap or leave the grid

enemy watershidden until you fire

Enemy waters: the computer places its fleet when you press Start battle.

sunk none yet

afloat carrier 5, cruiser 4, frigate 3, submarine 3, patrol boat 2

place your five ships, then Start battle: the computer hides its fleet and you fire first

Turn log, newest first

no shots yet

the computer aims from its 0 results only

layout saved in this browser

Turn: placing ships
Your hits: 0 of 17
Computer hits: 0 of 17
Sunk: none yet

Click or tap a square, or use the column and row pickers with Place or Fire. On the keyboard, Tab to a grid, then ← → ↑ ↓ move, Home and End jump along a row, Enter or Space places the chosen ship or fires, and R turns the ship while you place it. There is no undo once a shot is fired, since its result has been seen.

The rules, played out

Frigate across B2 to D2; cruiser down from H8carrier already on B2 to F2; rows end at 10
both rejected: B2, C2 and D2 are taken, and H11 is off the grid
Fire at D6 a second timeD6 is already a hit
ignored: still 8 hits, and it is still your shot
Hits on G1, H1, I1a 4-long cruiser on F1 to I1
3 of 4 hit, so not sunk; F1 sinks it, and the game ends only when all 17 cells are hit

Common questions

How do you play a battleship-style game?: Each side hides five ships on its own 10 x 10 grid: a carrier of 5 squares, a cruiser of 4, a frigate and a submarine of 3 each and a patrol boat of 2, 17 squares in all. Ships lie straight, across or down, may touch, and never overlap or leave the grid. The two sides then take turns firing at one square of the other grid, and each shot is called a hit or a miss. A ship sinks when every one of its squares has been hit, and the first side to sink all five ships wins. On this page you fire first, and a hit does not earn an extra shot.
Is this the Battleship board game?: No. Sea Battle is an original hidden-fleet grid game with its own name, grid, ship names and drawings. It is not the Battleship board game and is not affiliated with its publisher.
Does the computer cheat or see my ships?: No. The computer chooses every shot from what it has been told: the squares it has fired at, whether each was a hit or a miss, which of your ships it has sunk and the squares that ship covered, which the page shows you too for every ship you sink, and the lengths of the ships still afloat, which the rules make public. Its choice never reads the position of a ship it has not sunk; those squares are used only to call its shots hit, miss or sunk, the same way your shots are called against its fleet. On Easy it fires at random squares until it hits, then at the squares beside its hits, along the line once two hits touch. On Hard it counts every way the ships still afloat could lie among its hits and misses and fires where the most of those ways cross, favouring ways through hits it has not yet explained by a sinking. Neither level is perfect play.
Can ships touch each other?: Yes. Ships may sit side by side or end to end, but two ships never share a square, and every ship must fit inside columns A to J and rows 1 to 10. A placement that breaks either rule is refused with the squares at fault: with the carrier on B2 to F2, a frigate across from B2 is refused because B2, C2 and D2 are taken, and a cruiser down from H8 is refused because H11 is off the grid.
What happens if I fire at the same square twice?: The shot is ignored. Your shot count and hit count stay the same, it is still your turn, and a message says whether that square was a hit or a miss. The computer never fires at a square twice.
How do I place and turn the ships?: Pick a ship, then click or tap the square where it should start: it runs across to the right or down from there, and on a pointer or keyboard a preview shows where it will go. The Across or Down button, or R on the keyboard, turns the chosen ship, and a ship already on the grid turns in place when it fits. Placing a ship again moves it, Random placement lays out all five, and Clear takes them off. Start battle works once all five are on the grid. On a narrow screen the column and row pickers and the Place and Fire buttons are at least 44 pixels tall, so you never have to hit a small square.
Is my game saved, and can I undo a shot?: The game in progress, your ship layout and the computer level are saved in this browser after each change, when the browser allows storage, and come back when you return. A saved game that was edited outside the page, or damaged, is refused and a new game is set up. There is no undo once a shot is fired, because its result has already been seen. New game keeps your last layout on the grid so you can play again at once; once a shot has been fired in a battle, you press it twice to leave the game.
Can I play against a friend online?: No. This page plays one person against the computer on one device. There is no online matchmaking, no chat, and no betting or prizes, and your shots and ship positions are not sent anywhere.

One stated set of rules: a 10 x 10 grid, five straight ships of 5, 4, 3, 3 and 2 cells that may touch but never overlap or leave the grid, one shot a turn, and a ship sinks only when every one of its cells is hit. The computer aims using only the hits, misses and sinkings it has seen, never your hidden ships, and a repeated shot is ignored rather than counted or charged a turn. The grid and pieces are original, a game in progress is saved nowhere but this browser, and there is no betting, prizes or online matchmaking.