Nicole Scherzinger follows proper swim etiquette even when she's overseas -- always rinse after taking a dip ... even if you gotta hose off.
The former Pussycat Doll was seen enjoying the ocean in Saint-Tropez Sunday with her Bulgarian tennis pro boyfriend, Grigor Dimitrov ... who seemed more than happy to spray down his smokin' hot GF after taking a dive off their boat near the French Riviera.
He was diligent too ... making sure to get both her front and back, and just about everywhere else. Nicole, of course, returned the favor.
Makeshift couples' showers on the high seas ... c'est la vie.