Gwen Stefani made her Cannes Film Festival duties as a L'Oreal ambassador into a fun family affair, and she was spotted out on one of the many glamorous boats off the coast of France today. She sported a bikini and waved off the top deck with Zuma while Gavin Rossdale took their older son, Kingston, out for a spin on a jet ski. The little guy held onto dad from behind as they sped off in the water near Antibes, and later hot Gavin stripped off his shirt to give us a peek at those abs. The Stefani-Rossdales arrived in Cannes on Friday and have since been hanging out on the yacht, owned by Russian businessman Roman Abramovich, and checking out the local sights. Don't miss all the amazing Cannes Film Festival pictures and check back to see the action from the red carpets, premieres, and parties around the French city!