UPDATE: The world file: https://filebin.net/upr8aesd8depymo4

UPDATE 2: *Still unresolved. Apparently a user downloaded the world and aquatic mobs were spawning freely; and we were both using the same version (Optifine). Also, I've tried switching from optifine and still no fix.

UPDATE 3: Wow. I'm at a loss of words. After reinstalling and searching for a few more hours I finally went back to the spawn chunk (the home spawn from the screenshot posted by Josh) and found an oasis of ocean life. Squids, fish, dolphins. Everything. Even after the reinstall, there are absolutely no aquatic life other than the occasional drowned, however, in the spawn chunk there are. So I guess this issue is resolved for me somewhat, but still an issue.

My survival world I have been working on for the past few months has never once had a single squid/fish spawn and after finally requiring some black dye, I decided to look up the issue. The solution stated that an upgrade to 1.14.4 (was playing on 1.14.3 prior) would fix the issue. After upgrading, I searched far and wide and could not find a single fish/dolphin/squid still. I searched more and more, a mod on a form stated that the issue no longer existed in 1.14.4; but a user wrote that they had to find squid/other aquatic mobs in new chunks; not old ones. So, I'm currently at X:4,000+ (I have definitely never reached this far, maybe 1,000 at the maximum), while checking through oceans, rivers, streams, etc on the way. I've been searching around here for about an hour (and probably another hour of traveling) and there still is absolutely no squid, fish, or dolphins spawning. I'm checking oceans, ponds, everything. Making sure they Coordinates match where squids normally spawn; everything. Absolutely zero aquatic mobs spawning. I have seen drowned spawn numerous times, but none of the other mobs I stated above. Does anybody know any way I can fix this? Thank you.

Few more things to note:

-I doubt this is a mob cap issue; considering I've gone through numerous chunks. I kill any drowned I see.

-I also see turtles spawn, but on land only. Never have I see them in water. I also kill them on sight in order to ensure it's not a mob cap issue.

-I've never bucketed any aquatic life, so that can't be the issue either.