This career task is very difficult to complete. The buoy option doesn't work and its nearly impossible to find the exact right spot to click on in the ocean bay. The hitbox for the fish is extremely small and the camera needs to be angled at the exact right spot to click on it. I was actually sure it was completely broken until I came to this thread.
I'm on my fourth play-through of the Marine Biologist career. Something seems to have changed with this work task since the last time I tried it. In the past I was able to complete this task by clicking on sea turtles in the water (not the babies from the turtle hatching, that is different) or schools of fish that spawn in a few places around Mua Pel'am. On this play-through I haven't seen any turtles in the water in 2+ weeks of playing. The schools of fish still spawn a few times a day and I can still complete the work tasks by clicking on one of those.
There are two spawn points that have been working fairly regularly, where the schools of fish will spawn several times each day. I have been able to complete the work task at one of these two spots every time it has come up. One spawn point is in the lagoon near the waterfall and the second is on the other side of the island near what looks like a fallen pillar in the water:
You have to look carefully because there isn't any pop-up menu that shows up just by hovering the cursor over the fish. All you see is a small "gear" symbol and the menu does not show up until you click on the gear. As others have already stated, clicking on the Survey Ocean Wildlife option on the green buoy does not complete this task, and I wish they'd just remove it to avoid confusion.
