Tom kaulitz heidi klum on the beach

The supermodel, 51, showed off her behind in a cheeky thong bikini as she kissed her rocker husband, 35, before he climbed on top of her on the beach.

Heidi Klum and husband Tom Kaulitz packed on the PDA during a St. Barts beach day.!

Heidi Klum Splashes Around in Tiny Bikini with Husband Tom Kaulitz In St. Barts

Heidi Klum living it up and stripping down on a beach in St.

Barts ... wearing a tiny black bikini while splashing around with her husband, Tom Kaulitz.

The model enjoyed some sun, surf and sand Saturday ... going for a quick dip and engaging in a whole lot of PDA with her man -- sunglasses still covering her eyes even in the water.

After the two got their fill of the saltwater, they headed for the shore ...

Heidi Klum goes topless on the beach in St. Barts with husband Tom Kaulitz after his brother is evacuated in LA fire ; Heidi Klum flaunts bikini.

Heidi Klum was back in beach mode on St. Barts, showing off her incredible physique in a bikini with her hubby Tom Kaulitz at her side.

Heidi Klum and husband Tom Kaulitz packed on the PDA during a St. Barts beach day.

Heidi Klum turned heads in a cheeky thong bikini while soaking up the sun in the Caribbean alongside her husband, Tom Kaulitz.

Heidi Klum showed off her stunning figure in a tiny string bikini while on vacation in St. Barts with husband Tom Kaulitz.

revealing Heidi's whole ensemble.

HK's decked out in a tiny top and thong-style bikini bottom ... leaving little of her body to the imagination.

We've told you all about Heidi and Tom's St. Bart's vacay ...

with the two regularly hitting the water over the past few months -- and, Heidi even standing topless on the sand.

Call Her Daddy / Spotify

Heidi's talked about her love for going topless a lot ...

admitting on the "Call Her Daddy" podcast last year that her kids always have