Britney and Sean Preston Spears are spending some time vacationing in Hawaii ... and that bathing suit isn't really doing her any favors at all!

And can we talk about her feet? I realize that her hooves look like they are caked in sand but they are very unappealing to look at ... which is why I'm calling attention to them ... what, do you think I want to be the only one suffering this A.M.?

While Brit and SP are sunning themselves in Hawaii, Kevin Federline is home taking care of his business ... which looks like involves this mysterious blonde:

I suppose these pictures could be totally innocent ... maybe she's his cousin or something ... altho, I wouldn't necessarily trust K-Fed to behave around his own cousin.