Visuals: There's quite a few sub games during this Jam/Compo - this one is my favorite visually. The sunlight effect is well done, and visually looks striking when fish pass by to block your beams. That and the small touch of particle effects in the water gives a good full vibe to the game.
Music: You nailed the music! Great underwater vibes and an immersive theme.
Game mechanics: Simple but interesting mechanic to play through. On a longer challenge the only thing I can possibly think of adding is maybe mirrors or ways to make the shining between two submarines a bit more complex.
Only confusion: Without reading the instructions I was confused on what to do for a while. I kinda just shined the light on the sub. A lot of bad ADHD gamers like me miss instructions so maybe a little pop up on the first sub that said "click" would've resolved that. Not a big deal.
Overall, great job executing the theme and style of this game. You both should be proud!