Since updating to 1.16 prerelease 1, I've noticed that zombie piglins are now able to pathfind into water, even as far as 6 or 7 blocks beneath the surface. As someone who has been actively playing the snapshot versions, and has held zombie piglins in close proximity to water for while without seeing them once pathfind into it, I thought it worth noting. For further context, this is happening in a warm ocean biome, and is more of an amusing idiosyncrasy than an actual inconvenience, but nevertheless, it does appear to be a bug.