Re: Shower Pan
Small mosaic tiles, one inch tiles, set in epoxy and using an epoxy-fortified grout to resist cracking and leaking, probably would work well.
Personally I think I'd just go for white pick-up truck bed liner, which has some texture, can be applied in multiple coats, will be light and easy to clean with no grout lines at all. Can be used as anti-skid on the companionway steps, etc. as well. Not as good, but also not as hard on bare feet, as the kind that have sand or other spiky stuff in them.