One question what are you playing? GWX 2.1 or stock SH3 1.4?
IN SH3 1.4:
It's pretty easy to sink any type of ship in stock. Even in shallow water.
IN GWX 2.1:
Is it in shallow water? It is really annoying if you sunk a destroyer in shallow water.
Because, even though the bow is sunk, the stern is still sticking out of the water.
Maybe you should damage it more along the waterline to really sink it.
I hope this helps.
