I haven't actually used Halcyon itself, but have had great luck with water-based finishing products. The thing to keep in mind is that water-based does not mean water-soluble. These products are not like watercolor paints that will wash off. Instead, the finish components are in suspension in the water. When the water evaporates, the components merge, form a layer on the substrate and harden into an insoluble layer. In the past I've used water-based 2-part linear polyurethane marine paints. Some have lasted 14 years without needing a touchup.

As far as not being for use below the waterline, every finish product in my shop, except the Petit bottom paint, says that. As long as you don't keep it in the water you'll be fine. After all, every topside paint and varnish has to stand up to rain, spray and the occasional big wave.

Laszlo

Thanks  Laszlo. I used Brightsides on the bottom of my Passagemaker and it's also not supposed to be used below the waterline, though, of course, everyone does it for boats that don't live in the water. So I guess it's the same kind of thing. Well I guess I have a winter project set. Wonder if I can finish it by Christmas as it going to be for my granddaughter.

Thanks  Laszlo. I used Brightsides on the bottom of my Passagemaker and it's also not supposed to be used below the waterline, though, of course, everyone does it for boats that don't live in the water. So I guess it's the same kind of thing. Well I guess I have a winter project set. Wonder if I can finish it by Christmas as it going to be for my granddaughter.

If you have heated shop space it's a possibility. They build the WD hulls in a week at the CLC classes. Just work clean so you won't have to sand a whole bunch.

Laszlo

   Ha-learned that lesson on the Pocketship.,

 I used the Halcyon clear on a tandem CNC Vember kayak I built a couple of years ago.  It has held up fine but there is something about the clarity/color that I just don't like as well as Schooner varnish which I have used on my other wood kayaks.   I have not tried the Halycyon amber 

   I used TB Halcyon on a paddle board this winter. The board has only been used a few times this summer and stored indoors so I can't speak to how it will stand up to time, wear, and UV. I did want to chime in about surface quality and application. Because my project was a paddleboard there was a huge flat area to finish which allowed me to see every defect in the application. I had a lot of trouble achieving a flat, level finish. I tried cheap foam brushes, nice finish brushes, I applied a thin coat, I applied a thick coat, I applied thinned product, I applied unthinned, all had surface defects associated with self leveling. I finally figured out a method that yeilded a very nice level finish:

While the product is self leveling, it is intended to be applied quite thick (much thicker than solvent based varnish). If you don't apply thick enough you will see half leveled waves of brush marks even with full coverage. The application method I found to work best was to work in sections off of the wet edge and brush (cheap foam brush, I tried a nice finish brush but found the foam to work best) on quite a bit of product in one direction (overapply so it looks milky/cloudy), then brush at a right angle, then brush in the original direction again, and finally I would finish by brushing at a right angle from the original direction. The key to a level finish for me was to overapply the product at first, and then remove product with the final tipping stroke pausing periodically to scrape extra product from the brush back into my container as I was tipping. So basically I overapplied, then tipped/removed to acheive a level surface.

I was able to acheive a very nice level finish with this method on my final 5th coat, although I did have to sand down the uneven ridges after the first 4 coats as I figured out this application method. I would use this product again because of its low toxicity, and ability to layer many coats in one day, but if it doesn't stand up to time, wear, and UV very well, I would move on.

   Wow- thanks for the details! I'll be referring to this when I get to that stage. Picking up the kit tomorrow and then the fun begins. 

  I'm going to flame Halcyon. But first,

Generally, Total Boat offers great products.

It holds up great, 5 years (+?) and no degradation.

Reapply as many as 5 coats/day.

No smell.

Water clean up.

Comes in its own 'stop loss' bag.

Concur with Sam on getting good flow out, can be done, not easy.

The finish is repulsive, icky, ugly and cloudy. Feels like muck coming off the brush. Never again. Hard to overstate how much I hate the stuff.

Just one users opinion, try a small pouch first?

   I tried your method Samuelsjohns, but ended up with brush strokes. Perhaps I needed to sand down the strokes from earlier layers better. It's weird too, how a foam brush would leave brush strokes.  I am ok with the color and gloss of the finish, but really disappointed it's not a nice even finish. I can see where applying a heavy layer is needed, but then it's hard to keep it from running. It would probably work fine on a flat, level, surface but that's hard to find on a boat. On the other hand, I could never have finish the kayak in time for Christmas without it as I needed something low VOC with fast recoat time. That being said it looks fine from 10 feet and I had several people pass on compliments during my trip to take it to my granddaughter. 
 

So, based on my experience, I'd caution against it for the real craftspeople. I hope to improve my technique so I can use it again in the future with better results.
 

    Oh and one more thing. I can see another reason why people would not like using this product. I don't enjoy painting, but I do find using standard varnish very satisfying. It's not hard to get really nice results with just a bit of effort and the way varnish goes on is - pleasant. The way Halcyon goes on more like a water based polyurethane. It's more like painting. If the results were wonderful this would be  a small thing, but it is a bit of a negative.