Secondary explosion instant death

[Sniper297]

Odd thing I noticed when attacking unescorted convoys with the deck gun - ship blows up, sinks, a minute later I get all those messages "taking damage hull destroyed engines destroyed etcetera etcetera" then the you're dead screens. Don't remember seeing that until recently, but when it happened while submerged near a sinking ship it happened again.

Set up a mission with 4 docked tankers, drew range circles around them, then proceeded to test. At 300 yards commence firing with the deck gun, explosion after a dozen rounds or so, "enemy ship destroyed" message, no damage to sub. At 250 yards about 1 minute after the destroyed message comes the series of "you're screwed stupid!" messages.

Thought maybe this was a mod soup problem, most likely suspect bombs.zon so replaced that file with the original, same thing.

Went to my backup copy of original unmodified 1.4, copied that folder to desktop and copied the new mission with the 4 tankers into it, same results.

So the question, no damage if you're 300 yards from a sinking exploding ship no problem, 250 yards you take 100% damage? Is this new, or have I just never noticed it before?