Some additional thoughts about water operations:
1) salt water ruins all sorts of things with corrosion, and it gets everywhere and into everything, so it's best to stay in fresh water if you can
2) rough water is a very dangerous situation, period. Winds that are easy to handle on land can whip up waves that you don't want to cope with on water
3) extremely smooth ("glassy") water can be just as bad, because it is hard to judge height above it and landings can be risky
4) take-off distances can't match wheels on pavement, because of water drag
5) slightly submerged but hard to see obstacles can ruin your whole day
6) it is common to find other forms of traffic on suitable waterways (jetskis, boats, etc.) that you don't have to deal with at airports
Because of these and other factors, utility likely won't be what one might hope, and the conditions required for safe operation are a narrower set than one might like . It could be fun and a nice novelty, but one shouldn't expect to get a go-anywhere capable craft by putting floats on a gyro.