I have an idea to fix the continuity error of aqua pups!
what about instead of the retcon/continuity error of aqua pups,
Coral did choose to stay but was instead was half merpup half land pup, so staying in puplantis was just a matter of staying in her merpup form.
That explains how she can talk and transform on land.
Moby is half merpup too, but cannot speak because he hasnt been to the surface before.
Instead of the fistbump, Zuma and Rocky intrigue him (Moby saw them interacting and was interested in one of Rocky's invention ideas he was proposing)
so he follows them up to trash island.
Trying not to be caught, he leaps behind the large trash island rock. Thats when he transforms and gains the ability to talk.
Zuma and Rocky hear the commotion, but dont notice him sneaking away and shrug it off. They were just there for materials.
I know its a far fetched idea and might be confusing for the preschoolers but at least it fixes the main retcon from the original episodes.