Abstract The Sonic Kayak is a musical instrument with which to investigate nature, developed during open hacklab events. Kayaks rigged with underwater environmental sensors allow paddlers to hear real-time water temperature sonifications and underwater sounds, generating live music from the marine world. Sensor data is also logged every second with GPS, time and date, allowing fine scale mapping of water temperatures and underwater noise that was previously unattainable using standard research equipment. The system provides the paddler with an extra dimension of senses with which to explore the underwater climate, while enabling citizens to gather data for scientific research. The system can be used as a citizen-science data-collection device, research equipment for professional scientists, or a sound-art installation in its own right, and has been implemented in a public setting at the British Science Festival 2016, demonstrating the considerable advantages of adopting transdisciplinary approaches during project development. Here we present instructions for building the open-hardware and open-source software, tests of the sensors used, and preliminary data demonstrating applications for the Sonic Kayak in marine climate and noise-pollution research.