Ok, so I was trying some stuff in the new version of minecraft were we have all the new underwater blocks, and I think I have found that really very annoying bug. When you place a bottom half slab under water and you swim towards it from above, the game tries to let you walk on the block, because you hit it's surface, but as soon as you start walking (with contol still pressed) the game will make you start swimming again. So what will happen if you have a row of bottom half slabs is that you will constantly switch between swimming an walking. And it wouldn't have been such a big problem if the POV would'nt change every time that you switch between the two. Just to be clear: this does not happen when you swim toward normal blocks from above. I don't know which blocks are affected, but the slabs is defenitely one of them.