[headquarters]

Firstly - the gear needed to go down to svereal hundred meters depth 200-300) is more or less the standard looking diving gear - neoprene dry suit ,mask ,leadbelt,fins ,divecomputer, ventil system /respirator etc .-and tanks .

The quality of the gear should be outstanding at anything below 50ft imho or you are liable to do yourself an injury - but plenty of perople go down with older / cheaper stuff .(Thats not to say that older is poorer ! )

Its what is in the tanks that is the main issue as fas as I know ( got the open water advanced or whatsitsname).Regular compressed air can only be used to a depth of 42 meters (?) or the oxygen will drug you and you will take your mask off to kiss the pretty fishes before you sleep a in the gently rocking current at 70 meters depth .( Or so I have heard )

When you go down below a certain depth ( I guess its roughly 60 ft) you are on a clock .The longer you stay down ,the longer you need to stop at intervalls on your way up - hanging on to an anchor rope at say 20 meters for 15 min ,then at 10 m for 10 mins etc -these depths and times are variables .

The longer you stay down ,the longer you will have to wait before you can resurface .This is because nitrogene bubbles accumulate in the blodstream ,and have to dissipate before you resurface -the nitrogene bubbles expand the closer you get to the surface as the pressure decreases.I am told it can be hurtful and cause cardiac arrest if you get into an accident with this .

Decompression chambers are used for people who go up to fast , or for people that have been down so deep and so long that they cant very well decompress in the water .

I have PM ed you a link with various dive tables that can be downloaded .

For all you divers out there -I am aware that I only know the main principles and not the details anymore ..its been a while since my last dive .