One of the key aspects of tuning the OpenROV before a dive is getting the buoyancy correct. Inherently, the ROV is very cose to neutrally buoyant, but different components or batteries, salt or fresh water can make the ROV naturally want to float or sink.
So far, we've added weights to the threaded rods of the ROV when it's been too buoyant, but we've never had an elegant solution for the ROV being too buoyant.
John was having that problem with his ROV. Someone suggested using Ping Pong balls to help, but the challenge was finding a way to attach them So John created a ping poing ball holder!
It was designed in Inventor and I hope to see the design files online soon!