Thompson's
Water Seal? Don't do it!!!! It is a silicone-based treatment - once applied you are stuck with using silicone as all other coatings will not adhere over the top, and complete
removal is near-impossible short of heavy
sanding. (Silicone sealants also leave silicone behind which can prevent other sealants from adhering well.) If you are absolutely certain that this is what you want then proceed; just be aware that it will be a nightmare if you want to do something else later.
I started out using Deks Olje 1 & 2, and that doesn't last a year. At least it is easy to remove. Traditional spar
varnish, like Epifanes, looks great but also requires frequent sanding/re-coating. And even if well maintained it usually needs to be removed and replaced every few years as it becomes dark.
Cetol is incredibly durable and overcoating does not require
sanding. It is by far the best varnish equivalent I have found. The common criticism is that it looks orange after many coats, but this is because it is not being used correctly. To apply on bare
wood first use one of the pigmented versions, such as Teak or Natural, for the first 2 coats. Then switch to several coats of Clear Gloss, which is not pigmented. For
maintenance wash and dry the old finish and re-coat with Clear Gloss - never use a pigmented version again except to
repair any area that has worn through. I have used it this way on my fir
bowsprit for the last decade, and it always looks like a great varnish job (not the opaque orange look that happens with using just the pigmented version).
Greg