I know this is totally hijacking your thread, PearlieMae, but here's a monofin that I think would work super-well for that ghostly tail:

http://www.scubastore.com/scuba-divi...r-flow/31962/p

It's clear, so your fluke could be kind of translucent... Actually, I think the way it dries "clear" (you know, not actually clear) would lend well to the "phantom" effect.