Simplistic environment but really love the mood & feel. The inclusion of a hull breach repair task adds an important dimension. I wonder about the probability/physics of breach occurrence- is it affected by descent rate or direction of travel? Simply increases w/ depth? Are locations on the sub where breaches occur more or less likely to breach again? Lots to play with there. BTW breaches that can't be seen through porthole are tricky!
Also plenty of potential to add complexity to increase difficulty via introduction of currents, other moving entities, hydrothermal vents, gas seeps, etc. to the environment. Neat stuff!