I don't own any of these brands (Tsunami, Koozer or Seaboard) but I've seen the actual frames. They are pretty decent quality. From what I saw, they are pretty much the same product or came from the same factory and rebranded. And some small details to to make them different. I don't know if these companies are related or not but that's my observation.
I have seen dozens of builts using these 3 brands including the models you guys mentioned in the local FB bike groups. Handsome builts even. These groups are fixed gear, gravel bike and bike packing/touring groups. So it's pretty wide spread as well. Most of these builts were during the height of the pandemic up to now. But I've seen Tsunamis in the fixed gear group way before the pandemic. Before the pandemic, I got into getting one for a single speed setup but had to cancel it because I couldn't find a supplier who had my size. It was more of the timing, 'coz several months later, my size did crop up... but I already have an SS.
I haven't seen any in depth reviews among these builts but so far I've yet to hear/read any complaints and/or catastrophic failures. So that's a good sign.
