That depends on your training level and the type of equipment you use. Do not go deeper than your training permits you to do so.
- if you have your basic Open Water certification you should not exceed 60 feet or 18 metres.
- The recreational depth limit for diving is 132 feet or 40 metres with your deep diving and/or advanced certification.
- If you have a technical certification and are trained to use different gas mixtures you can go deeper than this.
Currently the Guinness world record for a dive on SCUBA gear was set by Ahmed Gabr, 41 on September 22, 2014 by diving to a record 1090 feet and 4.5 inches (link here). This broke the previous world record of 1,044 feet set in 2005 by Nuno Gomes.