Amazing that an 88,000 pound armored vehicle could swim so well.
We loaded up in a P5 in the well deck of a 'Gator Navy' ship (USS Alamo?) off the coast of Vietnam back in '69 for an amphibious assault. The Navy only flooded the well deck about 4 feet deep. Amtracs draw about 7 feet or more of water.
We went roaring off the stern and promptly dove about 10+ feet deep. The P5 had small slit windows up high in the troop compartment. We could see the surface of the ocean sparkling WAAAAY up there. Naturally, the gaskets on the front hatch/ramp were leaking and water was pouring in.
"I'm in a 45 ton steel box, 10 or 15 feet under water and it's leaking to beat the band!"
We finally popped to the surface and churned our way in to crawl up the beach. One on the other Amtracs sunk just before the beach in about 8 feet of water. Thankfully, the P5 had long overhead hatches, so everyone climbed out the top, safely.
Fun times!
;-)