This is a Significant Operational milestone.
The trials were carried out on the SS Bunker Hill using a Sikorsky XR-4 fitted with floats. 23 takeoffs and landings were carried out. The pilot was Col. H. Franklin Gregory who was an early advocate for the use of rotorcraft for military operations.
Source: "Vought-Sikorsky XR-4/HNS-1 First Shipboard Trials", Ken Bartie, VFS web page, Last accessed Feb 25, 2020