Royal Air Force Marine Branch
The Marine Branch (1918–1986) was a branch of the Royal Air Force (RAF) which operated watercraft in support of RAF operations. Just days after the creation of the RAF itself, the Marine Craft Section (MCS) was created with the transfer of Royal Naval Air Service (RNAS) vessels and personnel to the new service.
Source: Wikipedia — Royal Air Force Marine Branch (CC BY-SA 4.0)