Have now managed to find the Coast Guard log entry for this incident:

24/2/33 Report by Supplementary Watchman Owen Williams from Look Out Hut that he had seen a signal of distress from two seaplanes anchored in Nefyn Bay (S1230 and S1235 from RAF Pembroke Dock). Porth Dinllaen lifeboat was called out. Also Life Saving Apparatus Company with lifebelts and lines. No S1230 grounded at 1015 at Ty Coch. The Company assisted two men from the seaplane. It was then reported that one airman was missing, but he was seen immediately afterwards drifting towards the shore. He was rescued by lefebelt and line. S1235 was trying to beach at the Bwlch, which she did so at 1105, the airmen wading ashore. No lives were lost. The LSA Company was dismissed at 1500.

They must have been from No 201 Sqn. Southampton Mk II.