I made it to 216, but it didn't add me to the leaderboard D:
oh no, sorry about your awkward experience :D if you have any cost-efficient idea to help first time players to understand "they need to swim back to surface", we would appreciate it.
On last update, we add some signs with text at the beginning, hope it will help.
Please try again now and try to return to the surface, I assure you the game will drastically change :)