Having your home be partly underwater isn't a good idea unless you are living in the Seashelter from David Eltang. This shelter was designed to be able to be submerged during high tide.
The Seashelter from David Eltang isn't really a home. It is more like a wildlife observatory. You can view sea critters when the tide is up, and then explore the seabed on foot when the tide retracts. This shack was designed to be used along the coast of Denmark and can sit two and sleep one. Looks like you just got a new vacation destination.