I'd cut off most of those roots (all but a couple of inches) before planting in a very coarse textured, highly porous potting medium. It's going to have to develop the kind of root system than can extract water from a solid growing mix rather than roots that may or may not be able to obtain dissolved oxygen from water. I don't think of avocados as being aquatic plants.

Next time, plant the pit directly into the kind of medium I described.