(04/07/01)["Breathing underwater."] I am preparing a staged area for some meeting. I am cleaning off a table and helping students place agendas and information on the tables. Part of the event involves diving underwater to great depths. I have a breathing mask on and I dive in, but can't get to the bottom, because the pressure is too great. I come back up and get some advise that if I switch the toggle switch from the top chest pack to the belly pack when nearing the depths, I will do better. I do that and find I can reach the bottom and breathe fine. I also see some residential people a family who lives down there and they are so acclimated they don't need any breathing apparatus.