My daftest death.
I'd loosed a couple of eels at a large Merchant and she was refusing to sink, so I surfaced and started using my deck gun on it. A few shots later and my WO shouts "ship spotted". I'm thinking "I know there's a ship numpty, I can see it!" So I carry on shelling the ship. The next thing the WO shouts is that the ship is under attack.It's 1940 I can see that the Merchant is unarmed. Just as I'm thinking about throwing the WO overboard, shells start exploding all around. I look in the direction that they are coming from and see a destroyer hurtling towards me, shooting all cannons.
30 seconds later and I'm dead.
Now when my crew are using their deck gun, I'm scanning the horizon looking for trouble.