When trying to create a farm, I realized that water blocks next to non-full blocks ie. tilled soil, half slabs, grass paths, etc. cause a magnetism effect where the player is dragged into the water block if they're adjacent. This was not me falling off blocks either, I was at the center of an adjacent block and was still pulled in.

EDIT: I realized this is true not just with water, but air blocks next to paths and farm tiles also pull the player in. Has not been tested with soul sand or slabs yet, but I think this might be a general problem with these block types