If this flight was not carrying fare-paying pax, ie. that he was paying for going form A to B, there is not a requirement for floats from the regs. as far as I know.
It might be in the company's Operating Manual, but if this was a ferry with two crew, then it is up to the pilot to choose the route that he will be comfortable with.
Now, how smart it is to fly over large bodies of (freezing) water without suits,dingy and floats are a different discussion, but that it's illegal is unlikely.
It looks like really bad luck, having to fly (further) out over open water due to the exercise, and then have an emergency which dictates a forced landing. What are the odds of that?!