For those with fold3 access, the war diary of the USS Sturgeon, starting on 28 April 1942 is here:
https://www.fold3.com/image/29441490
Basically, they received the order to check for the RAF men on 28 April. They proceeded to Tjilatjap. On the night of 29 April they tried to run a boat in close to shore but had motor problems and had to hoist the boat back on-board and then submerged. The engine was worked on during 30 April and that night they tried again. The boat returned at 2:30 am on May 1. They had run the small boat close to shore, tried signaling the letter "P" some 40 times and then actually used a megaphone to call out while within 50 yards of the shore and then used a spotlight beam. The Lieutenant in charge of the small boat was Chester Nimitz, Jr, son of the admiral.