Unio is a small danish company with subsidiaries in Spain and Poland, selling the service of designing floating homes, hotels, offices, etc. They have one finished design (Icon) of a 100 ton low-floating home, though it is obviously designed for fresh water and not the open ocean. They detail their choice of construction and materials, which I think is interesting.
This is interesting. I live nearby so I just tried to e-mail them about having a look at their house if they built any yet, but the mail returns with an error. Is it a dead company? I’ll try to call them tomorrow.