Holding breath while aiming and swimming under water should be a time-limited operations.

This could be represented by a new icon in the bottom right-hand corner, perhaps lungs that show how much longer you can hold breath for. When lung capacity has been reached, the following should occur:

• If swimming, lungs flash red and health take immediate damage until the character swims to the surface
• If holding breath for aiming, immediately stop holding breath and the character has 'puffing' sounds for a few seconds while they catch their breath

These changes would make both activities much more realistic.