One could argue anything, but not successfully.One could argue that an underwater photography system is a single item as any one piece cannot complete the designated activity alone. So your 3k camera with a lens and 2k housing and a strobe is well over your $5k exemption. I realize it's a bit far fetched and I don't think many people will have to deal with it, but the abuse of this type thing that occurs in Mexico is well documented, and so it warrants paying attention to.
My lens is separable from my camera, my camera is separable from my housing, the strobes ae quite distinct, etc.
Why are you looking for fringe exceptions and unrealistic scenarios? Just to argue?