Sea Battle rules
Sea Battle is a guessing game for two sides. Each side has a grid of 10 by 10 squares, with columns A to J and rows 1 to 10, and hides a fleet on it. The sides take turns calling one square of the other grid. The answer is miss when the square is empty, hit when a ship is there, and sunk when that shot hits the last square of a ship. Whoever sinks the whole enemy fleet first wins. The game is widely sold as Battleship®, a trademark of Hasbro; this page is not affiliated with Hasbro.
Rules for the pen-and-paper game vary, for example in the ships of the fleet and in whether ships may touch. This page uses the fleet below. Every ship lies in a straight line across or down, never diagonally, and ships never overlap.
| Ship | Squares |
|---|---|
| Carrier | 5 |
| Cruiser | 4 |
| Frigate | 3 |
| Submarine | 3 |
| Destroyer | 2 |
| Fleet in total | 17 |
With Ships may touch set to No, there must be at least one square of water around every ship, also at the corners. As a result, when a ship is sunk, the squares around it cannot hold another ship, and the page marks them as clear on both grids. With Yes, ships may lie side by side. Each side fires one shot per turn, hit or miss, and you fire first.
The computer levels
- Easy fires at random squares it has not tried yet.
- Normal fires at random until it scores a hit. Then it tries the squares next to the hit, and once two hits lie in a row it keeps going along that line until the ship is sunk.
- Hard works out where the ships still afloat could be. For every ship it counts each position across and down that does not cross a miss or a sunk ship, adds one to every square the position covers, and fires at the square with the highest count. After a hit, only positions through that hit count, so it closes in on the ship fast.
We let each level play 1,000 games against random fleets and counted the shots it needed to sink all 17 ship squares. A perfect game takes 17 shots and the worst possible takes 100.
| Level | Average shots, ships may not touch | Average shots, ships may touch |
|---|---|---|
| Easy | 87 | 95 |
| Normal | 50 | 59 |
| Hard | 38 | 44 |
Strategy tips
The smallest ship covers two squares next to each other, so it always covers one light and one dark square of a checkerboard. If you hunt only on the squares of one color, every ship must be hit at least once in at most 50 shots. Once you have a hit, try the four squares next to it, and after a second hit follow the line in both directions. With the no-touch rule, skip the squares marked clear around sunk ships. When you hide your own fleet, avoid patterns the other side can guess, such as all ships along the edges.
Pen-and-paper play
Download PDF gives two pages, one per player, on US Letter or A4. Each page has a grid called My fleet, where you draw your ships and mark the shots you receive, and a grid called Enemy waters, where you mark your own shots: a dot for a miss, an X for a hit. The checklists next to the grids list the fleet with a box per square to tick off hits. Sit so that neither player can see the other's page.
How to play Sea Battle online
- 1Choose the computer level and whether ships may touch.
- 2Place your five ships: pick one, choose Across or Down, tap a square. Or press Random placement.
- 3Press Start battle and tap a square on the target grid to fire. The computer answers with its own shot.
- 4Sink all five enemy ships before the computer sinks yours. Play again keeps your fleet so you can change it or start right away.
Related guide
Frequently asked questions
How do you play Sea Battle?
Each side hides a fleet on a 10 by 10 grid. You take turns firing at one square of the other grid. The answer is miss, hit, or sunk when the last square of a ship is hit. The first side to sink the whole enemy fleet wins.
Which ships are in the fleet?
Five ships: a Carrier of 5 squares, a Cruiser of 4, a Frigate of 3, a Submarine of 3 and a Destroyer of 2, so 17 squares in total. Ships lie in a straight line across or down, never diagonally.
May ships touch each other?
You choose. Rules for the pen-and-paper game differ on this. With Ships may touch set to No, no ship may sit next to another, not even corner to corner, and the squares around a sunk ship are marked clear because no ship can be there. With Yes, ships may lie side by side but still not overlap.
What do the computer levels do?
Easy fires at random squares. Normal fires at random until it hits, then tries the squares next to the hit and follows the line once it has two hits in a row. Hard counts every way the ships still afloat could lie on the board and fires at the square that the most of them cover.
How do I place my ships?
Pick a ship in the list, choose Across or Down, then tap the square for its left or top end. Tap a placed ship to pick it up, tap it again to turn it. Random placement puts the whole fleet down for you. Start battle unlocks once all five ships are on the board.
Can two people play?
On screen you play against the computer. For two people, download the PDF: it has a page per player with a grid for your own fleet, a grid for your shots and a checklist of the fleet.
Can I play with a keyboard?
Yes. Tab to a grid, move with the arrow keys, and press Enter or Space to place a ship or to fire. R turns the selected ship while you place. Every square has a label such as "B7, miss" and the status line announces each shot.