ship help

[skullduggery bones]

Can anyone give me a few pointers regarding ships.
I wonder why sometimes when you've blown the ship to smithereens and the red bar has gone but the ship is still there with the counter at zero. Why hasn't it sunk???
Also I have a galleon at the moment which seems to sail at the pace of a snail!! Is that just because its a bigger ship?? (even with full sail it seems slow)
And do the broadside cannons upgrade themselves the more you use them??
And lastly, I've bought some chain shot cannon balls before but I can't think for the life of me where I got them from as I've run out and need some more.