The octopuses are always visible and they are always in the same spot every game. Thus this achievement is pretty straightforward. Some are really hard to see and youll easily miss one of them since there are so many.

The parrots are only visible for a few seconds and after that they go invisible for a while, im guessing its around 10 seconds. They are always in the same spot every game though so just waiting for them to show at the spot will work. Some are really hard to find and youll easily miss one of them since there are so many.

In order to find the seahorses you first have to click an item, after that the seahorse pops up on your screen somewhere. The easiest one in my opinion since there are not that many and items you can click are indicated with an different cursor, which makes it easier to find.