Iron Golem floats in water, can swim, and spins

Video of the end result of the glitch: https://www.youtube.com/watch?v=t-uE-yTCxi8

UPDATE: Video of glitch occuring: https://www.youtube.com/watch?v=jf40ErfAxAY

Basically, an Iron Golem will walk upto the lightpost in the village, take a right and walk right into the water. Unlike when pushing an Iron Golem into the water, the Iron Golem this way starts floating and spinning, as if trapped in a whirlpool.

Note when I nudge the Iron Golem at 01:25 in the first video, it bobs slightly while moving, as if he is swimming and then goes back to spinning.

Video of two Iron Golems spinning with Party Parrots: https://www.youtube.com/watch?v=PPkNeBeIHb8