My buddy and i have just finished a dive to 15 m/50 ft 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 timea. wait and check our no stop times on our computers periodicallyb. use the dive computer plan mode, if our computers have themc. use a dive planning appd. check the rdp table or erdpml