In the past few years, we have covered a bunch of awesome coding robots for kids. The Lebot is designed to work under water. It has a modular design, magnetic connectors, waterproof components, and a floating WiFi antenna. This kit can be used to build a robot boat or submarine.
Lebot’s app is based on Scratch, so your kids can program the robot via drag & drop. This project is getting funded on Kickstarter. Expected to ship in December.