Concern with the heavy casualties in the first 24 hours led Schmidt to commit the 21st Marines from corps reserve. The seas proved to be too rough. The troops had harrowing experiences trying to debark down cargo nets into the small boats bobbing violently alongside the transports; several fell into the water. The boating process took hours. Once afloat, the troops circled endlessly in their small Higgins boats, waiting for the call to land. Wiser heads prevailed. After six hours of awful seasickness, the 21st Marines returned to its ships for the night. Even the larger landing craft, the LCTs and LSMs, had great difficulty beaching. Sea anchors needed to maintain the craft perpendicular to the breakers rarely held fast in the steep, soft bottom. “Dropping those stern anchors was like dropping a spoon in a bowl of mush,” said Admiral Hill. Hill contributed significantly to the development of amphibious expertise in the Pacific War. For Iwo Jima, he and his staff developed armored bulldozers to land in the assault waves. They also experimented with hinged Marston matting, used for expeditionary airfields, as a temporary roadway to get wheeled vehicles over soft sand. On the beach at Iwo, the bulldozers proved to be worth their weights in gold. The Marston matting was only partially successful--LVTs kept chewing it up in passage--but all hands could see its potential. [Illustration: _“Portrait of the Artist as a Young Man,” acrylic on masonite, is by Col Charles H. Waterhouse, wounded in his arm on D+2 and evacuated from Iwo Jima._ Marine Corps Combat Art Collection ] Admiral Hill also worked with the Naval Construction Battalion (NCB) personnel, Seabees, as they were called, in the attempt to bring supply-laden causeways and pontoon barges ashore. Again the surf prevailed, broaching the craft, spilling the cargo. In desperation, Hill’s beachmasters turned to round-the-clock use of DUKWs and LVTs to keep combat cargo flowing. Once the DUKWs got free of the crippling load of 105mm howitzers they did fine. LVTs were probably better, because they could cross the soft beach without assistance and conduct resupply or medevac missions directly along the front lines. Both vehicles suffered from inexperienced LST crews in the transport area who too often would not lower their bow ramps to accommodate LVTs or DUKWs approaching after dark. In too many cases, vehicles loaded with wounded Marines thus rejected became lost in the darkness, ran out of gas and sank. The amphibian tractor battalions lost 148 LVTs at Iwo Jima. Unlike Tarawa, Japanese gunfire and mines accounted for less than 20 percent of this total. Thirty-four LVTs fell victim to Iwo’s crushing surf; 88 sank in deep water, mostly at night.