Bella Hadid knows how to make a splash ... it just helps when she's got a luxury yacht to jump from.

The supermodel showed off her figure in a thong bikini Monday while relaxing with British Formula One racing driver, Lewis Hamilton, in Monaco. He had no problem showing off his bod either.

Bella's been living the yacht life quite a bit since arriving in Cannes last week.

It's unclear if she's dating Hamilton or they're just hanging out, but as we can see ... Bella likes to jump in with both feet.