[sub] has returned to [location1].
The ocean has claimed [sub] and its crew.
Succumbed to their injuries
Bled out
Drowned
Suffocated
Crushed by water pressure
Burned to death
You have succumbed to your injuries.
You have bled out.
You have drowned.
You have suffocated.
You have been crushed by water pressure.
You have burned to death.