Oh wow. I feel incredibly stupid. Thank you for taking the time to explain and try to help.
Aquatic mobs still tend to be kinda glitchy but seeing as there's already a lot of users bringing them up (a couple being the ones you shared) I think it's safe to say I can focus on other things.
Herobrine?
Dude I have the same issue and it's insane!
I can confirm this is definitely not a false report. I've seen these everywhere, it's not just happening it's an extremely common occurrence.
I am. It's intentional? I'm fine with that but they're less rare lol. Seriously they're everywhere.
Oh wow I didn't think of that. I'll double check and see if that's the issue. Thanks for the suggestion!
My brother and I are having the same issue!
I didn't have pictures this time because my brother and I were just having a blast! I will add them when I get them.
This happens in both Creative and Survival. I was goofing around in Creative here but the aquatic mobs will get stuck in rivers too. Oceans don't have this problem as often. I'm unsure how Guardians are affected but Elder Guardians are kinda wonk. Don't know if that's intentional or not.
This is an issue as of 18.0.0. Very annoying to deal with.