Doug - All Great point. I don't know enough about metallurgy (as it turns out, knowing nothing about something is just not enough ;)). My thoughts were basically that if big cheap stamped knives flex and last on a fishing boat for years, then a shovel out of that steal would also last. I think the knife I'm imaging sitting on the boat is a dexter russel 31628, but its steel is only described as "stain-free, high carbon steel." That said, it might be that in a thicker form it would get brittle, or be prohbitivly expensive.
As far as full fiberglass, I'm not sure I've handled anythign with that. I was imaging the glass cored plastic exteriored cheap mauls and axes I own. Full glass may well be nicer, but I remember anchor pickup buoys giving me unpleasant splinters.
Alas - I'm sad to hear my idea is unrealistic.
Re properly maintaining a common steel shovel in a marine environment, agreed, it can be done, but there is that leave it and forget it beauty if stainless and plastic.
On the smaller version, it might be huge w/backpackers, etc. As for me, the current size is just fine. I have to take a picture of how I mounted it in my Subaru. It is super dorky, I love it.
R