Which sentence is correct?
Adam has swum with sharks and lived to tell us about it.
Adam has swam with sharks and lived to tell us about it.
Swum is the participle for "to swim" so "he has swum" is correct.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.