Our family of 3 lives on a 36 foot boat in San Francisco Bay. We have around 400 square feet of living space, but about 50 feet of that is the enclosed back deck that is rarely used (except for storing bikes), so really we're in more like 350 square feet.
There are a lot of things we absolutely adore about boat life, and we make it work, but I won't lie, we'd love to have more space. As our kid is getting into the teen years, we talk a lot about moving onto land. Our plan theoretically is to do so in 2 years, but we run through the calculus of places to live in the Bay Area that have good schools + are affordable + a reasonable distance from work almost daily it seems, and haven't come up with any solutions that we think will work. So we may end up leaving the Bay Area for good. Until then, we plan to enjoy amazing views and sea life, and have fun taking the boat out when we can.