The sound that plays when you collect coins as your air rapidly depletes is so ominous! It reminds me of the seatbelt indicator in a car.
This was fun! It was pretty challenging, but every death felt like my fault. I constantly wanted to push my limits and see how much gold I could bring back in a single dive. I love that the game encourages me to optimize my dives, and punishes me for being greedy. It's a good loop.
I would be interested to play a version of this where running out of air (or getting spiked) reset you at the top with a time penalty - I might be a little more willing to take big risks without the threat of a game-over.