[header] How to stay underwater longer [title] Start a cardiovascular exercise routine. [step] The best way to increase the amount of time you can stay underwater is by increasing your cardiovascular ability. By committing to a cardio training exercise routine, you'll increase your body's ability to process and use oxygen. 
[substeps] Commit to running, powerwalking, using an elliptical, or another cardio activity. Exercise 3 to 5 times a week for at least 30 minutes.