So, there's 18 fish/sea creatures in total (plus an 19th secret/bonus one which isn't tracked). Each time period has three fish available, with one being a little rarer and/or harder to reel in that the others. You only need six fish (excluding the secret fish) to proceed with the aquarium "quest", but if you want to see everything you'll need to catch all 18 fish. You can track this on a paper map found via the metal detector on the beach.
To fish, wait for the fish to bite, it'll give a little pinging animation, and right-click (image 1), then spin the "reel" on the right-hand side against the direction the arrow is travelling in the top-right-hand-corner (image 2)

For some of the tougher fish, if you happen to have a graphics tablet, I found it easier to use that instead of a computer mouse to spin the reel. It came in very useful against the "Drawing of a Fish", which I was having a lot of trouble reeling in.
A quick way of avoiding the "encounter" with the ominous figure that appears and can kill you during the night, is to have the Camera item out. If you take a photo, it'll despawn the ominous figure. You can also do this every time you load into a map at nighttime even if the ominous figure isn't in your field of view, you'll hear a screeching sound if the ominous figure was indeed on the map.
Though, unfortunately you can't do that until you have the Camera item...
| Time | Available Fish/Creatures |
|---|---|
![]() Daytime 1 |
Colisa Lalia Jantic Fish Nautilus |
![]() Daytime 2 |
Peter Panini Seahorse Singing Fish |
![]() Daytime 3 |
Eel Reddest Fish Ever Sea Man |
![]() Nighttime 1 |
Pirate Skele-Fish RC Ship |
![]() Nighttime 2 |
Big Worm Crab Star Fish |
![]() Nighttime 3 |
Crate Jelly Drawing of a Fish |
There's a 19th secret/bonus fish which does not contribute to your total fish count; you don't need to fish it up to unlock anything (as far as I'm aware).
It can be found by fishing during any of the nighttime time slots. How rare it is, is a mystery though at the moment. Some folks have played through the game multiple times and said they haven't encountered it, but I managed to fish it up on my first play-through and mistakenly assumed it was one of the regular 18 fish until I checked the paper map and realised it wasn't on there...
It's also currently not known if there's some specific condition one needs to achieve before the bonus "fish" will show up. If there's more investigation into this and it's discovered, I'll update this section with more details.
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