On D-Day Seabees were the first ashore as Naval Combat Demolition Units (NCDU). Their task was to remove German defensive beach obstructions built to impede amphibious landings. "They came under very heavy fire, but placed and detonated all their charges. The gaps created permitted the assault to hit the beach. To facilitate this Seabees placed pontoon causeways over which the assault could access the gaps." "Seabees also brought their Rhino ferries, a motorized adaptation of their modular pontoon boxes. With them, vast amounts of men and material went ashore. For the American sector Seabees assembled piers, and breakwaters into Mulberry A. It was a temporary port until French ports were liberated. Even after weather disabled the Mulberry, Seabees continued to get thousands of tons supplies and troops ashore."