The stock Bensen with floats has a pretty lethal configuration. The floats act as drag chutes, located far below the aircraft's CG. They try to pull the gyro into a vertically nose-down position. The faster you fly, the worse this effect is.
The problem existed even with the old 1930's autogyros, which were otherwise quite stable. One float-equipped autogyro of that era flipped upside down in the air. Probably because of the nature of its rotor suspension, it reverted to upright flight and landed safely. A modern gyro with an underslung teeter hinge will not fare so well once it's upside down and experiencing reverse flow into the rotor disk.
A gyro friend of mine got into float Bensens. He flew his first in the towed gyroglider configuration, then added an engine. He then experienced an uncommanded dive into the waters of Long Island Sound. He landed in the hospital, but survived. There have been other nose-dives of float-equipped Bensen-style gyros whose pilots did not make it.
Bottom line: a float gyro needs to be designed from the ground up, and tested first with models and them the real thing. A safe design would be a big R&D project.
The stock land-based Bensen is not a particularly user-friendly, stable craft. It, too, tries to flip upside down under certain circumstances. It can be made safer with frame alterations and different tail surfaces. As Wasp says, the stock version killed scores of people (the kill yield got up to about one a month for awhile in the late 60's).
Other scores of people have accumulated thousands of hours in them, but you have to watch your back when flying one. There are safer designs on the market today.