Atacking the Sea

Hello;

As Great Britain I have 4 Destroyers atacking some submirines, but they aren't dealing damage to them since the stats show that they are bombarding the sea, even with a naval bomber above the area to find the enemies.

If submirines are supposed to hide forever they are invincible.

Edit: Also I've lost 2 DD atacking these subs and when the battle ended they just hid again, so I'm bombarding the old info of where they were.