I had tested this with Creeper riding Zombie, Creeper riding Iron Golem, Armour Stand riding Zombie, Ravager riding Phantom and Skeleton riding Spider, the last was the only one that didn't dismount, probably because the spider floated on top of the water
I had tested this with Creeper riding Zombie, Creeper riding Iron Golem, Armour Stand riding Zombie, Ravager riding Phantom and Skeleton riding Spider, the last was the only one that didn't dismount, probably because the spider floated on top of the water