There are a few Japanese army tanks on Saipan, which are relatively small and are made of fairly thin metal plates. There are 2 American Sherman tanks in the lagoon, which are significantly larger and with much thicker armor. The story I have heard (but have not been able to substantiate) is that someone mis-read the tide tables, so as the Americans launched the invasion along this beach they became totally waterlogged, bogged down "sitting ducks" for the Japanese. I have been told that there were originally several tanks here, but that after the war all but 2 were hauled off (to where, I don't know). Apparently it was decided to leave these 2 here as a sort of memorial. If anyone else has more information on this, please leave comments!