Alessandra Ambrosio's Making a Splash with Sofia Richie ... Look, Don't Touch!

Alessandra Ambrosio's on an endless yacht vacation that just gets better and better ... courtesy of her smoking hot friends, including Sofia Richie.

Lionel's model daughter is hanging with Alessandra and co. off the coast of Ibiza. They've been going cray cray on vacay -- holding hands leaping into the water, dancing with each other ... and showering on deck. Lots of showering.