A Chinook helicopter and a Royal Marine rigid-inflatable boat (RIB), off Studland Bay, Dorset, UK. A Royal Marine rigid inflatable boat dangles from a Chinook helicopter during a hazardous 'Underslinging', a method of quick extraction and insertion of waterborne personnel. The daring procedure involves the helicopter lowering strops and coming down to just above sea level at which point the boat and crew will push through the down draft under the helicopter and attach the lines to the bo