Gisele Bündchen and boyfriend Joaquim Valente are turning up the heat this summer … playing in the waves in Costa Rica and looking stronger than ever.

In new pics, obtained by TMZ, the couple is seen frolicking in the waters off Santa Teresa, on the Pacific Ocean side of Costa Rica, on June 27, along with her children. The model is spotted rocking a chic blue bikini with white polka dots, looking as stunning as ever.

An eyewitness tells us Gisele and Tom Brady‘s kiddos — Benjamin and Vivian — were all smiles as they played in the sand with Joaquim … taking turns racing one another along the beach.

Gisele’s clearly in full sun-soaking mode … about a week prior to these pics, she was seen in a tight white swimsuit paddleboarding with friends in Florida.

You’ll recall, Gisele and her jiu-jitsu instructor boyfriend welcomed their first child together back in February … although it’s unclear if their son made the voyage with them to Costa Rica.