I'm just wondering, can people travel cross continental after the war because virtually all aircraft were destroyed or ran out of fuel(apart from enclave and at least one NCR vertibird) so how did people like moriarty(Irish) and tenpenny(English) get here? The sea would be heavily irradiated and I wouldn't be surprised if FEV affected sharks or something which makes boat unlikely... So how? Any suggestions?

Why are you assuming the oceans would be heavily irradiated? It wasn't (Pacific Ocean) in Fallout 2 and in Fallout 3 the Atlantic Ocean is only slightly irradiated and you have to remember that Bethesda just desided that radioactive water would be a coolz to have, even though its been 200 years and no other Fallout... anyways the oceans aren't heavily irradiated. Even if they were it wouldn't stop ships from taveling.

Also why would FEV make super sharks and other sea monsters? In Fallout 2 there is an Oil Tanker that later sales off into the sunset and in Fallout 3 there is that fairy boat going around.

The most likely way Tenpenny got to America was by ship. To bad Bethesda didn't give us any information about how he got to America, why he came to America, what was it like where he came from or even made it clear in the game that he came from across the oceans.

Oceans wouldn't be irradiated. Most of the radiation comes from fallout, which is dusty padticles so that goes no more than several feet down. Then the water is always moving, so some fallout will just dissipate like usual, and some will wash onto shore snd then dissipate.