So apparently, "Spar Varnish" was originally developed for sailing ships. It was used to protect the wooden beams that supported sails aboard the ships. Its original remit was to both protect the wood and be flexible, appearance was of minor importance. Over the years, it appears, the term "spar" has gone quite far. The term's now applied, like so many I've spied, to a coat that is good for a boat. While varnish, and poly, and shellac and spar continue to be used fairly interchangeably, they are all their own chemical entities.
Basically, I'll be looking to find a coating that can withstand both UV rays and water. I don't need the flexibility of a true spar, but in case anybody is curious, the original spars were developed to withstand wind-induced flexing spars on sailing ships. UV protection and protection from water were the other two components of the three qualities desired. Appearance was not part of that trifecta.
Just posting up some information I found. I'm sure there are scores of great products that could be called "spar", and since I have at least a year to learn, I'll select a finish and be sure to keep this updated when I find it.
Cheers,
Tim