But, if you look at it this way: in the bookverse, when Legolas heard the cries of the seagulls, he was struck with the urge to go to sea. So my logic is that when the elves left Middle Earth, Legolas included, he was reborn as Will Turner in the regular world. And that totally explains why he was found floating in the sea.
It's just like how Gandalf was Dumbledore between the time he "died" on the LOTRverse and the time he "died" in sixth year of HP!!
*rereads random rant* .... I need a life.