I tried to hide a barel in some water by throwing it into it. The barrel just vanished. I was a bit confused as this works fine in 0.60, so i got some more barrels.
They all disappeared when i threw them near water (rivers or ponds, not tested with ocean). At some point i saw one barrel, flying through the air, hit the ground out side the river, and then falling through the ground of the river.
Throwing a barrel on normal ground worked somewhat fine for me (the barrel was behind me for some reason), at least it didn't fall through the ground.
Later i tested it with a wheel, i guess it was an offroad wheel, and it was showing the same behaviour.