There is no better way to learn electronics and robotics than building and programming your own things. The Erle-Boat is a smart aquatic vehicle built with a Raspberry Pi Zero. It uses ROS and autopilot software for various modes.
The boat weighs 770 grams when fully assembled. You are going to need a Pod Racer boat, battery, PXFmini with WiFi 802.11ac USB dongle, and a few other simple components to complete this project.