How much submarine dive into deep water?

All military submarines dive into deep water. The deeper they can cruise,the harder they are to find. I call 'deep' any more than 120 feet down, but most modern military submarines can operate as deep as 900 feet, many even to 1500 and possibly more.

There are now many civilian submarines (shallow divers) which show tourists the undersea reefs and fish life. These generally operate between 30 and 90 feet down and I doubt that any could safely dive deeper than 200 feet at most.