Then I made a nice open document grid for Scrabbleship play:
Also included is a PDF version. Print it out, then cut it in half, and each player marks off ships in the lower half of the sheet: One 5-square ship, one 4-square, two 3-squares, and a 2-square ship. I think you can place them diagonally if you like. Remember to get the half of the sheet that corresponds to which way you face the board. Notice the H row isn't even marked out--it's the row the first word goes in, and neither player will have ships in that row. I drew a line through it on my Scrabble board.
Keep your sheet hidden. Try to only play words in the enemy's side of the board. You don't want to hit your own ships or give away spaces where your ships aren't... you want to hit your enemy's ships!
Long words are nice for stretching out into enemy territory, and it's interesting the way the board grows versus in a traditional Scrabble game.
If a word played hits one or more squares of a ship, those squares should be announced, and can be marked off on the upper part of your score sheet. Niki and I played it before so any hit to a ship sinks it, because otherwise, it's pretty easy for a ship to be unsinkable because it's impossible to put words into all of the squares it occupies.