[2020] Tuna

They actually do talk about the different types of water in the dev diary[forum.paradoxplaza.com]:

Sunset Harbor features 4 types of fish, all of which prefer different conditions. Anchovies thrive in still, shallow waters, salmon prefer shallow water with a flow, shellfish require deep and still waters, and tuna need deep, flowing water. This means one single map might not always have the required conditions for all types of fish.

If you mean how to get the water like that, then I would recommend opening up a map like MrMiyagi's Sunset Harbor and look at how he achieved the different types of water. He's a great map maker and good at getting water to behave, so it's an ideal place to get inspiration.

https://steamcommunity.com/sharedfiles/filedetails/?id=2034806081&searchtext=sunset+harbor