As stated here at airvectors.net, early F4F Wildcat variants featured a life raft in the aft fuselage behind the pilot, which was discontinued in later production.
Does anyone here know at what point in F4F/FM/Martlet production the fuselage life raft compartment was eliminated?
You might want to read this bit from the linked AirVectors article:
"An inflatable life raft was carried in the fuselage behind the cockpit and could be ejected on ditching, but it was later deleted in favor of a raft in the pilot's survival pack. Inflatable flotation bags were fitted under the wings for ditching at sea, but after the bags spontaneously inflated in flight a few times, leading to crashes, they were abandoned."
It appears that the fuselage life raft was retained at least throughout F4F-3 production (not counting the 100 aircraft delivered as fighter trainers in early 1943), whereas the underwing flotation bags were discontinued early in -3 production.