I’ve had my Zhik HydroMerino base layer (top and bottom) for a few years now, and I’m really happy with them. In fact, I haven’t gotten my hands on a piece of Zhik (rhymes with ‘psych’) sailing gear that didn’t impress me.
Pros
I also have some Smartwool and Icebreakers merino base layers, and these compare very favorably. The weight of the material is similar to the lighter Smartwool base layers, and the construction of the seams is similar. I have some of the heavier Smartwool as well, and it’s certainly cozy, and nice to sleep in when it’s cold instead of having to add another layer. It’s a slimmer fit than the Smartwool that I have, and very similar to the Icebreaker’s ‘Bodyfit’; the torso is cut longer than either which helps keep it from riding up if you’re sitting or bending over. I have worn them for days at a time while sailing and they resist even my smellier-than-average pits quite well, which is true for all the merino base layers and one of the biggest appeals for me (and those around me). Durability has been great; the Smartwool I have seems more prone to pilling and the Icebreakers have broken a bit of stitching some of the seams (mostly from me trying to cram my feet into the legs).
Cons
The only real downside to the Zhik and other merino base layers is cost. Polyester is much cheaper material for base layers, but stinks up quite readily. The merino is at least as durable, works better, and resists smelling, but that comes at a cost. The Zhik base layers are slightly more expensive than either the Smartwool or Icebreakers, especially if you score the others on sale, but the durability has been great and the fit is my favorite of the three, particularly for the top.
Conclusion
If you’re day-sailing or racing in relatively warm, dry climates, you can probably get by with polyester base layers like the Henri Lloyd ones linked about, and just don’t try to get multiple days of use out of them unless you’re single-handing. If you’re going offshore or sailing in wet weather, I’m certainly glad to have my merino base layers.