Diving the Yankee Clipper Jacks with Dmitry

Dmitry and I went diving this morning. We entered the water South of the rocks in front of Tower 2 and swam on the surface just past the swim buoys, where we descended and began slowly working our way East. We ended up at the Jacks, though I really don't understand how. We followed them about 2/3rds of the way along the Jacks, when Dmitry indicated that he had only 1100 psi left.  We turned the dive and headed back.  He was at 500 just as we left the reef and he shared air with me back to the sand before the beach, when we had sucked my air down to 500 psi.  Seemed like a calm easy dive and I was expecting a dive time around 135 minutes, but it all changed when Dmitry got near the bottom of his tank.  Water temperature was 84 degrees; Dive Time was 107 minutes.  My SAC rate was altered when I shared air with Dmitry, but calculated out to 17.74 psi/minute.  RMV was 0.46 ft3/minute.