When I was SCUBA diving a year ago at a reef of the cost of Destin Florida, I observed a very strange creature. One of our guides said it was a "Spanish Dancer", however traditionally a Spanish Dancer is a colorful mollusk and this only shared some charateristics. IT IS NOT A SPANISH DANCER. Hopefully you folk might have some thoughts on it.

It was a dark purple (or blue or black) creature. My thoughts are that it was a sea slug or mollusk or some kind. It had a tube like body roughly 12 inches long and running along it’s back were two long fins (almost wing like). It floated and moved slowly by waving it’s fins. It moved very gracefully and glided from reef to reef.

Any thoughts???

What u described sounds like Nudibranchia species. However, there are so many different species and based on info given, I am not able to help you identify.
However, u have seen the real thing itself and if u do a yahoo search on Nudibranchia, and select images, u will be able to scan through the numerous images and see for urself.