Bathtubs

Different sizes and shapes of particles behave in different ways on beaches and there are folks (mainly British, I suspect) who have spent their careers looking at ridges of disc-shaped cobbles and bands of spherical pebbles found on shingle (gravel) beaches.

Based on this limited sample of an unusual sediment type, I have found that cast-iron bathtubs on southwest facing gravel-sand beaches in central Puget Sound tend to wind up upside down and are left projecting a few inches above the beach surface. I am not sure if this is generalizable to other types of bathtubs or other types of beaches, but I am absolutely sure this is pretty much irrelevant to just about anything.