The water is just as clear at 100m as it is at 10m or 1m. This is a missed opportunity for a great immersion making effect that is sure to spellbind new players. By making the water turn rapidly darker as you descend downwards you can give players a great feeling of diving deeper and make them "experience" the increasing masses of water that is above them. Sitting at 50m underwater and seeing a bright blue water fog is very immersion breaking. At this point the water should be very dark since it is blocking the sun.
It would be also be great if diving too fast verticaly would give a slight concussion effect to simulate pressure. This again would make diving a more powerfull experience for players and maybe even add some extra tactical considerations when fighting other divers. As far as I know this is a feature that should be easy to implement, but then again I am no developer :)