The keel bulb that’s filled with air, not lead

A stabilizer system for workboats using a canting, air filled bulb keel has been claimed to potentially allow 40 days more per year of offshore operations in rough weather.

https://www.maritimejournal.com/news101/vessel-build-and-maintenance/ship-and-boatbuilding/the-keel-bulb-thats-filled-with-air,-not-lead