It would seem that you might have to sell your body to make this. To make it totally transparent, I would go with a clear resin. Although that will probably yellow with age, but there are UV additives I believe which will help with the longevity. Most of the clear resins are going to be the polyesters (less expensive than the polyurethanes). Polytesters require resperators and gloves, nasty stuff, but nice and clear if you get the right one.
As far as the molding goes, I don't think you can get a resin to set in a full body alginate mold. You might want to consider doing a plaster mold of the body, that way you can wax and release the plaster and cast the resin right into the mold. If you need to use alginate, then you should do a plaster casting, take a rubber mold, then cast the resin into the rubber. Most resins don't do well setting up against moister, alginate is mostly water.
here's a site that might help
http://users.lmi.net/drewid/resin_faq.html
And then maybe just google 'clear resin casting' see what else you can find.
Good luck!
~N