Avani Gregg is making a splash in Croatia ... and these bikini pics have us ready to walk the plank right behind her.

The TikTok superstar struck a series of sultry poses while perched on the edge of a plank above crystal-clear water ... rocking a blue-and-white string bikini that did plenty of the heavy lifting.

Avani balanced on the narrow platform like it was her personal runway, serving up smoldering looks for the camera while the stunning backdrop tried -- and failed -- to steal the spotlight.

The social media sensation may have been walking the plank ... but judging by these shots, she's sailing straight into bikini perfection.

Check out the gallery!