When I was last in Florida, I witnessed two incidences of broken free-diving fins -- in one case, a fancy-schmancy SEAC carbon fiber one, north of 400.00 -- while preparing to dive, off of a crowded boat.
Apparently, it was clumsily stepped upon, presumably do to its large-and-in-charge, ungainly size, while the prospective diver was turning; twisting; or what-have-you, while on board. Of the second case, I only saw its broken result, on my return, and an unhappy diver, packing up his gear.
Much swearing ensued . . .