My buddy and I have just finished a dive to 15 metres/50 feet for 60 minutes. We want to return to the same site and depth and stay another 60 minutes. We can ______________ to see about how long we have to remain at the surface to have enough no stop time.

Unfortunately man does not have the ability to survive in the aquatic environment. To overcome this limitation, techniques were developed (which allow man to submerge during a certain period) called diving. Many people practice this technique professionally, in which case the breathing supply is composed of a mixture of various compounds - such as air, nitrox, heliox, trimix, among others - received through an umbilical tube. This entire process is monitored by a surface-mounted control station.

The case shown in the question, is a professional dive, by description, in which case the speaker of the paragraph and his friend should periodically wait and check each other's stop times on their computers, use the computer's plan mode. If your computers have them, use a dive planning application and check the RDP or eRDPML table if you want to know how long they have to stay on the surface to not have enough time to stop after diving 15 meters / 50 feet for 60 minutes.