Yes, Yes, Yes. Fbsport air products (airtracks) are waterproof. You are free to have fun with them in the water, or in the snow.
Fbsport airtracks are made from durable Double-Wall Material, which is 10mm-thick commercial grade PVC tarpaulin. And more importantly, reinforcements are made for all seams for better air-tightness and durability. So you don't have worries to use them in swimming pool, or in the sea.
Tips: Do remember to wash the airtrack by fresh water, and keep it dry before storage.