Our mission is to develop a solar powered ocean platform suitable for a single family to live on and so stable it is more like a floating island than a typical boat.
The people at Siemens have developed a very powerful but lightweight electric motor. With 4 of these you could make a big quadcopter that could carry some number of humans. We will see humans on quadcopters in the next few years. The prop below is sized for a fast moving airplane. For a slower quadcopter the blade would be another foot or two across and a little flatter angle.
For short times you could use batteries or long times a turbine/generator. If all you want to do is go from a floating home 12 miles out to land and back, batteries would probably work fine. If you want to go far, then turbine/generator will be needed but cost more.
You can take an existing quadbike and drive on water, as shown in this video:
If you used a quadbike with 4 wheel drive, bigger tires, a mud-tire tred, some safety floatation, it could work very well. The tire below works well for pushing water. The bike would have to be designed to withstand saltwater, which is probably the real hard part of this idea. But it could be done and would be fantastic to drive around the ocean at high speed. So commuting from your floating home to someplace on land could be very fast and a lot of fun. If you are not needing to go far, a 4 wheel drive electric might be easier to make resistant to salt water. Also, if you have a solar powered floating home you would always be able to charge up an electric bike.
Another video with several guys doing it many times:
