They are correct, it will blister and peel in spots if left in the water repeatedly for more than a weekend at a time. 

How are you planning on using your boat? If you take it out for a few hours or even all day and then pull it out of the water for storage, then a topsides paint should be fine. That's how I use mine and have had no issues with bubbling, etc. Keep in mind that topsides paint on boats that stay in the water still gets wet when the boat is underway. It's just not meant for extended immersion.

After about two weeks of immersion, the Brightsides will go soft, definitely.  It's really unusual for any of CLC's smallcraft to be in the water for that long, which is why Brightsides is perfect for 99.8% of our builders.  Kayaks get pulled up on beaches, dinghies hauled up on docks or motherships, and so on.  (A caution about Brightsides immersion has always been on our Brightsides store page.)  We'll keep putting that paint on CLC demo boats as we have for 20 years.  Anyone who's been to a CLC in-water demo sees how much those finishes are abused, and how well they're holding up.

I towed an Eastport Pram as a tender behind my cruising boat and 7-10 days of immersion never softened the paint.  

It's all beside the point, though.  Once you're keeping ANY boat in the water for two weeks, salty or fresh, you need some sort of herbicidal bottom paint to prevent algae or barnacles.  Bottom paint should be applied directly to the epoxy, not atop other paint.  PocketShip has Trilux 33 on the bottom.

John and all .. thanks, and my boat will thank you

I going for Brightsides

I have a Skerry that I had originally planned to only put in the the water when I was using it--always a few hours at most.  Now I find that I have a place (fresh water) where I can keep it in the water for several days or even weeks, so I have ordered some antifouling paint.  I noticed in John's post, though, that I should not paint it over my existing topsides paint, but sand down to the epoxy instead.

How important is this?  What problems will it cause, especially in fresh waterr?  I was hoping to sand the year-old paint down pretty good, but not off completely.   My reasons are not only laziness and impatience, but also the worry that I might sand off too much of the epoxy in places--something I definitely want to avoid.  I'm really hoping I can avoid sanding off every bit of the paint.  

I painted the hulls of my kayaks and the foils of my Skerry with VC Performance Epoxy. This stuff is slick, hard and tough. They tell you not to wait too long to sand it and they are serious.

It has to go over epoxy, not paint. Look it up.

Well, thanks for the info, but my question is about standard antifouling paints, not VC Performance Epoxy. 

D D, you may want to start your own thread. I was responding to the OP's issue.

As I'm completing my Passagemaker, I'm trying to plan ahead for the possibility that I might be able to leave it at the dock for extended periods during the summer, in saltwater in coastal Maine. Does anyone have any suggestions:

1) as to bottom paints to consider (and are there now any bottom paint products which could appropriately be continued above the waterline), and

2) how to go about finding and applying an appropriate waterline - or do I simply throw the boat in the water with an apporpriate load and spread some something in the water around the hull to leave a mark??

Any and all suggestions would be greatly appreciated. Many thanks! 

   I leave my Skerry moored in the  local bay from the end of May to the end of September/middle of October - the bay is in the Eastern Mediterranean. Leaving it in saltwater for at least 4 months, aesthetics don't come into it. The bottom is anti-fouled. 

I use a Turkish brand, Tekno Marin SPT which is white and much the same as the hull paint. I'd rather have a hull free of fouling than have it looking nice and performance suffering. 

I guessed at the waterline and then went a wee bit higher up the hull with the anti-foul. You'd be hard pressed to notice the change of paint. 

 Not wanting to hijack the thread but i guess there is no other way to communicate with a forum member, so my apologies.  Yambo, where abouts in the med are you?  We are moving to Sardinia in the early 2017 and taking the NE Dory i now have under construction, unless my son wants it and then I will simply build another one..

   I find it is NOT very durable. Am considering a two part.

   Hi oceanluvr, I wouldn't worry too much about the thread hijack, it's quite old (but resurrected by profitz). I live a few miles south of Marmaris in Southern Turkey. Moved here in 2006 and no regrets. I don't know Sardinia and it's a ways from here but I wish you all the best for your move and future there.

I had an Orkney Longliner in the UK but didn't bring it here but life is more relaxed and an outboard is noisy smelly and polluting. I prefer more natural propulsion methods now so built the Skerry.  :)

   Thanks Leesville. I was wondering about two part paint myself - but I've never worked with those products before. Do you (or anyone) have any thoughts on their plusses or minuses?

The downsides of 2-part paints:

1: They are expensive.

2: The fumes are more hazardous (especially if you spray).

3: Once you mix them, you have to use them right away: no saving any leftover paiont for the next coat.

I have sprayed a couple of cars with 2-part acrylic urethane auto paint, and the last issue is a big concern, becasue good auto paint is even more expensive than 2-part marine paint.  Also, if you run out of paint halfway through a spray session, things can get dicey, since you have to take a break to mix more.

Doug