Can cob be water proof? I want to build a small house boat to homestead on the river bank and on top of the river? If needed I am willing to use on partial home. I would like to create an all or mostly natural house boat.

It would be heavier and require more flotation than most materials. It doesn’t seem like it’d hold up as well either.  It might work. I have owned boats, but I have no experience with cob.

Are you talking about a houseboat and a separate structure on land?

You might use bambo or native cane at least for the boat, maybe with palm or grass thatching. I’m not sure what part of FL you are in.

I wouldn't use cob for boat building. If you were looking to do interior walls natural, wattle and daub might be a good idea. Cob is not waterproof, but will soak up moisture and crumble apart. As previously mentioned, cob is also very heavy and not ideal for floating. You can make water resistant clay plasters and waterproof lime plasters called tadelakt, but I would stick to wood for boat building.

How about stick built with wool as insulation?