By “self release” do you mean by hydrostatic release at XX m. WD?
No I don’t think that is a requirement on aircrafts.
I was thinking more along the lines of the mass evacuation systems installed on High Speed Crafts, similar to this one:
For WIG: shut installed on exit door and life raft ejected from an enclosure next to it. (with HR if required)
Back in the day of flying boats they were boats when taxing or in contact with the water, as soon as they were airborne they were an aircraft. With a hovercraft the skirt remains in contact with the water so it is classified as a watercraft.
In my opinion it is an aircraft relying on ground effect to remain airborne. No different to a flying boat flying very low but relying on aerodynamics to remain airborne.
I wonder how much went into classifying WIGs as subject to CG regs only. They should be treated as a boat while the hull is wet and as an aircraft when the hull clears the water; no different than a low flying PBY. Naturally the manufacturers are against this as it drives up the cost of operations.
WIG aircraft are required to keep clear of other craft (2001 amendments Rule 18) . Pilots operating sea planes have to be familiar with the collision Regulations. I know a Royal New Zealand Air Force pilot of a Sunderland Aircraft.
Then they’re not SOLAS compliant, are they?
I stand corrected. IMO and ICAO together with the USCG have classified anything that can not fly above 500 feet as a watercraft. There are a couple of contributors on this Forum who by their posts would seem to be qualified to operate one.
Generally the majority of operators would be drawn from the aviation sector with additional training to a lower grade marine qualification but it is open to mariners to cross train to a aviation ticket.
There are a few aircraft that can release liferafts from inside the plane, but it is not automatic IIRC.
I count on someone dragging the thing out the door with them myself.
Here is a link to the Ocean Flyer.
IMHO trying to classify these things as boats is beyond insane. I have flown in ground effect over the water for fun, you gain about 10 knots or so from reduced drag 
The plane is still an airplane, it flies exactly like it does out of ground effect but a little slower. It does not magically start handling like a boat in any way. Besides for that, it is far harder and more dangerous than flying at altitude. Ground effect fades away with altitude and is considered gone at half a wingspan. You are flying low enough to hit bridges, power lines, sailboats, and freighters. You are low enough to put a wingtip in the water in a tight turn. You cannot get within 500 feet of any person, which would include boats with people in them, and the FAA will sometimes decide a lot of boats in one area is congested and then it is 1,000 feet.
If I progressively overload an airplane, before I get to the point it won’t take off at all I get to the point it will take off but not leave ground effect. If I then described my new overloaded airplane as a boat, maybe the FAA would leave me be and maybe they wouldn’t. Now I am flying down the river in a plane that cannot climb and weaving all over the place trying to miss various obstacles without turning sharp enough to dig a wingtip in and kill myself. Not a really fun day.
If I get REALLY brave and head out into the ocean I will learn that ground effect is calculated on SMOOTH surfaces. 20 foot seas might cut into it to the point I might be lucky to be 20 feet above them.
Lastly the 500 foot rule is idiotic. If you can get to 500 feet high than you can get to 1,000 or 5,000 too, you are out of ground effect. I suspect someone is figuring out that some super autopilot will be at work here artificially limiting the “boat” to 500 feet and maybe doing radar-aided nap of the Earth flying like some military planes do. At that point I could just go program the nearest 737 to not go above 500 feet and roar up and down the river at 250 knots (speed limit below 10,000 feet) scaring the shit out of everyone with the N number painted over and a boat sticker and numbers from the DNR put on the nose instead. I can give the finger to the water cops too, what are they going to do about it?
edit - if someone builds these out of aluminum they will be beat to shit by low altitude turbulence and corroded like a zinc guppy by the salt air. The old-time flying boats need a LOT of upkeep.
More - are maritime classification societies going to try and regulate specialized aircraft? That should take them maybe 50 years or so to organize 
Others are also developing WIG crafts for passenger transport:
Video presentation:
