Unless it’s changed since I got banned like 18 months ago then buttons should already stay on the cannon if you go underwater as long as it is all part of the submarine. But if you mean use a button on a cannon while that button is touching water which forces a block update which then breaks the button then I’d recommend just making it an enclosed area before you go underwater which eliminates the problem. I had some submarines that did pretty well in battles and went underwater fairly often and the buttons never broke due to water

Also if you mean firing a cannon while it is underwater then idk what to tell you. I think there either used to be torpedoes or it’s been suggested several times but I’m not sure the exact reasoning why it was removed/never implemented

This is not an unban appeal but it’d pretty rad if I got unbanned anyways *wink wink*