One of the basic rules of flying over water is that you need some kind of raft if you're out of power-off glide range from land. Does that also apply to seaplanes or amphibious planes?
Here is an answer I found after a few minutes of looking up regulations online.
Federal Aviation regulations require carriage of FAA approved floatation gear when operating under Part 91 for hire (FAR 91.205(b)(12)), but Part 91 flights not conducted for hire are not required by the FAA to carry floatation equipment. It is worth noting that local authorities, including state, county and municipal authorities, may require that all vessels, including seaplanes, carry U.S. Coast Guard approved floatation gear on board.
Found on the https://www.seaplanepilotsassociation.org/resources/faq/operations/ website.