Right now, players rely on "phantom buoyancy" by adding pivots, hinges, or rails that exploit a bug that causes subgrids to create extra buoyancy, which can actually cause heavier creations to float higher in the water. From a pure creativity standpoint, this is a good option because it lets players create artificial buoyancy to make seaplanes and other creations that would float higher if they were made from lighter materials, and the voxel nature of the game makes it impractical to simulate thin aluminum airplane fuselage vs. heavy boat hulls.

The downside of this issue is that using robotic parts for their intended purposes, such as adding a crane to a ship, or other simple mechanical changes, can create so much phantom buoyancy that that part of the creation floats unrealistically high in the water, requiring the designer to either remove the crane or attempt to work around it by adding weight, etc. But phantom buoyancy appears to increase with higher-mass creations, so workarounds are buggy and limited.

Maybe if the phantom buoyancy was fixed so robotic parts didn't create magic floatation, a "float" or "buoyancy adjustment" block could be added that served this creative purpose in a way that didn't feel like a bug exploit. Then players could both add buoyancy as they feel is needed, and be able to use robotic parts without the unintended downsides and weird side effects?