It depends on your comfort level. But to qualify as a deep dive, it will have to be at least 60 ft. And unless its changed , you will be required to make at least two dives of 60 ft or greater to earn your deep certification. My instructor said we would shoot for 100 ft. And we made it with no problems. But, if I, or my dive buddy would have stopped him, He wouldnt have pushed us. The first thing he told me in my advanced class was, "That anybody can call off a dive at anytime", that means before,or during a dive , you should be able to call the dive . Period. If your buddies dont agree, I would find new buddies. Its important to stay within your comfort level.
Keep it fun and dive safe, Kenny