When a magma block is placed underwater, a whirlpool bubble column is generated. When soul sand is placed under source water blocks, an upward bubble column is generated.

What Minecraft block pushes you up in water?

Magma block: it's found in the nether or in ocean ravine, and when placed underwater creates a bubble stream that pulls you down. Soul sand: it's found in the nether, and when placed underwater creates a lifting bubble stream.

Do magma blocks do anything?

The third, and perhaps most useful, is that magma blocks will deal one damage every half-second to any living entities standing on top of them, but won't destroy items. By shoving mobs into a pit lined with magma, you can easily kill them off in large numbers.