Epoxy anything is good.
An excellent timber sealer is "Everdure". First released 40 or 50 years ago by Epiglass. Still available under the International brand from Bias/Witworths etc.
Follow their instructions re sealing treatment for marine timber applications (first coat thinned with epoxy thinners, 50% from memory), then reduce % with additional coats. Brilliant!
Maybe there are other good products available now too, and I have to move with the times...
Cheers
Brendon