Not to discourage new answers, but this question is answered by u/kookingpot in [this answer from our FAQ] (https://www.reddit.com/r/AskHistorians/comments/2uw1dc/who_were_the_sea_people_that_invaded_egypt_in/coc89qp/).

In addition to u/kookingpot's answer, see my responses to Tell me about the Philistines vs others in the Levant 1200 to 800 BCE and What do we know about the so-called Sea People's origins?