Minecraft wiki entry for Drowned, associated text: Drowned are not considered as aquatic mobs, instead, they are considered as undead, unaffected by impaling enchantment.‌[Java Edition only]
A drowned chicken jockey floats to the surface because the chicken it is riding floats, causing the drowned riding it to burn in sunlight during the day, resulting in a chicken in the middle of the ocean or river where the drowned jockey spawned in.‌[Java Edition only]
In Bedrock Edition, drowned have a 3D outer layer. This causes their heads and arms to look larger than in Java Edition and causes rendering conflicts with armor, particularly helmets.
Like spiders and endermen, drowned have eyes that appear to glow, although they do not produce light.