I put a satin finish (System 3 WR-LPU) on my Shearwater 14 and I really like it.  But I've always prefered a satin look over gloss; it's a personal preference. I like it because it doesn't have as much of a glare in full sun either. 

You can find two photo of the finish on the Shearwater here (also the unfinished deck of the Wood Duck I'm working on, just ignore that photo): 

https://plus.google.com/photos/113605413461236703013/albums/5744305396072259105

I believe that you can sand and apply gloss over a satin finish or visa versa, just like applying another coat of finish.  I have done this on inside wood with polyurethane finish, but have never tried it on a kayak. It would probably work best to apply the same brand in the different sheen unless you let it fully cure before you switch, just to be safe. 

Kathy

Yes, you can put gloss over satin and vice versa, however you have to keep in mind that satin varnish has absolutely no UV inhibitors so you must put down at least three coats of gloss first. And the gloss has to be a marine type, i.e. Captains, Gold Spar, Epiphanes, and not spar varnish from the big box stores. 

George K

Thanks for the info folks.  Thats a suprise to hear that the satins don't have UV coverage- important info for sure.

Hickory

I know that the WR-LPU does have UV coverage in any sheen, but I don't know about varnishes.  Best to check with the manufacturer.  System Three also makes a spar urethane in a satin finish that has UV protection (CLC sells this type). 

I'm going with System3 Satin Spar Varnish (over 3 coats of a gloss varnish-Petitts Hi-Build).  They say you don't need to resand between coats if you recoat in the 12-24 hr timeframe.  Glory be.

Some satin varnish's do not contain UV filters- like Interlux Goldspar satin, which is thus intended for interior use only, but most of them do.

Hickory

Epiphanes.  The best protection and avaialble in all finishes.  Watch application temperatures and thin accordingly for proper leveling.