D+1 landings. Black Beaches 1 and 2 made up the southern shore of the island and were not used. The airstrip, running roughly east–west, divided the island into north and south. Marine Corps battle planners had expected the normal rising tide to provide a water depth of over the reef, allowing their draft Higgins boats room to spare. However, on this day and the next, the ocean experienced a neap tide and failed to rise. In the words of some observers, "the ocean just sat there", leaving a mean depth of over the reef. A New Zealand Army liaison officer, Major Frank Holland, had 15 years' experience of Tarawa and warned that there would be at most 3 feet depth due to the tides. Shoup warned his troops that there would be a 50–50 chance that they would need to wade ashore, but the attack was not delayed until more favorable spring tides. The supporting naval bombardment lifted and the Marines started their attack from the lagoon at 09:00, thirty minutes later than expected, but found the tide had not risen enough to allow their shallow draft Higgins boats to clear the reef. Only the tracked LVT "Alligators" were able to get across. With the pause in the naval bombardment, those Japanese who had survived the shelling were again able to man their firing pits. Japanese troops from the southern beaches were shifted up to the northern beaches. As the LVTs made their way over the reef and into the shallows, the number of Japanese troops in the firing pits slowly began to increase, and the volume of combined arms fire the LVTs faced gradually intensified. The LVTs had a myriad of holes punched through their non-armored hulls, and many were knocked out of the battle. Those 'Alligators' that did make it in proved unable to clear the sea wall, leaving the men in the first assault waves pinned down against the log wall along the beach. A number of 'Alligators' went back out to the reef in an attempt to carry in the men who were stuck there, but most of these LVTs were too badly holed to remain seaworthy, leaving the Marines stuck on the reef some off shore. Half of the LVTs were knocked out of action by the end of the first day. Colonel David Shoup was the senior officer of the landed forces, and he