The photo was taken on 5 October 1931 from HMS Ark Royal (which became Pegasus to make way for the new carrier of the same name). The aircraft is not exactly a Nimrod but is the H.N1, originally named the Norn or Naval Hornet which served as the prototype for the Nimrod as S1577.
After it had served its time, S1577 was used in a series of flotation tests to see how long it would remain afloat in the event of a ditching. Flotation chambers were fitted in the fuselage and upper wing centre section.
In the photo, the aircraft has just been lowered into the water where apparently it remained above water for an hour. Presumably it remained attached to a crane so that it could be hoisted back to the surface.

Самолёты на фотографии: Aircrafts on the photo: Hawker Nimrod - ВеликобританияUnited Kingdom - 1931