tips on making holes in sunken warships?

[Evilhorde]

Hello everybody,
I am very new to model shipbuilding and I am ambitiously thinking about sinking several warships in my fishtank. I have purchased a number of 1:700 scale WWII warships and I am trying to find some tips, links or even just some good pictures to give me an idea on how big of a hole to create or how to do it in a semi-realistic way. I realize that 'perfect' damage is an art but I really don't require 'perfect', I just need 'okay'.

[Timmy C]

For your consideration: viewtopic.php?f=59&t=151881