Very fun game you got here! It's very enjoyable but imo the controls are a little slippery and take some getting used to but one you get a grip on them the game is a blast!

This game would be great if you had an entire aquarium-sized monitor to play on. As-is you just can't see far enough and the enemies are way too fast compared to how slow your fish is, so you just can't get away if you're unlucky. And the game becomes way too much luck in regards to what fish you can eat and that one of those giant monsters isn't already on your tail, with no possible way to get out of the way, in some cases.

Lives were added to maybe help a bit, but does no good really, seeing as when you die you just go back to the smallest-sized fish anyway.

--edit--

I see what you mean about the lives thing. The game does become much more playable once you've eaten 20 fish but before that it's really unfair.

Also, I should have pretty much all the medals except that Leviathan medal, yet the game only awarded me 2 of the medals so far. So even your strategy of pinging the server every 5 minutes is not working, as far as keeping the medals goes.

Fyi you need around 1700 fish to complete the game.
I got the sudden death medal although I played normal mode....
All other medals unlocked as they should. My highscore was not recorded though...
Edit: Just tested. The sudden death highscore works.

It was pretty fun, the medals partly work.. Even though I won the game I didn't get the Dombaegi or killing of the children of pride (I assume you mean win the game on normal). I assume that because newgrounds medals seem to time out. Tried reloading the page and game and they didn't appear. I didn't even know when I started the game that there were medals anyhow so no big whoop to me.

Number of fish of different sizes seems a bit off, the first few times I played I had a heck of a time finding fish small enough to eat. So you may want to ballance that a bit. After making it further through the game It looks like the smaller fish distribute randomly throughout the level. When you are tiny with a tiny FOV it is a really bad idea to leave the bottom, because off the bottom it is easy to get trapped in swarms of large fish. I would suggest grouping the smaller fish in one area so we don't have to evade for... I think first round I went about 10 minutes without being able to catch a fish I could eat before I died (didn't catch any). Almost closed the game right there. Second round I swam to the top to see if the small fish were on top. Died a bunch there. Third round i finally started getting smaller fish. Fourth round I killed it. But yeah, work on the distribution.

Another thing, the bubbly green around fish.. You know that looks like they are poisoned right? It doesn't look like a happy one up thing. I actually avoided those fish (and even the bubbles coming off of them) until I accidentally hit one and found out they were 1 ups..

Overall I had fun, like many of these games it can be difficult to tell what you can eat or not. I did notice as well that there were multiple sizes of each fish so you couldn't just rely on the type of fish until you were big enough to eat the largest one. Whales were particularly difficult as (to me anyhow) the ones that were small enough to eat still looked longer than me to me.

Keep up the great work!

Your game clearly reminds me of this one:
https://www.newgrounds.com/portal/view/605618
but that game is much better in many ways. The main problem is that the smaller fish you can eat at the very beginning are awfully scarce. It already tells the player that it will be too long than it should be thus not that enjoyable. And it even poses a risk that the game will disconnect from NG not awarding the final medals.

PS

After playing it for a while I managed to upgrade my shark to higher levels, so it is manageable. So far I can tell that the medal for eating another shark is not working. You should have tested all the medals by yourself before releasing the game.