In the log, at about 944.8 seconds, I see the throttle stick being held down. Looks like about 60% to 70% down. During that time, the Phantom descended about 10 meters while the stick was held down (about 14 seconds). I believe this is the point where the OP was bringing it down to the boat. There's more down stick at 960.33 through 961.8 and another batch of 10% to 30% down throttle from 965s through about 969s although those last ~5 seconds of down stick only resulted in a ~1.5m drop in altitude according to the baro. This would be consistent with more controlled, slower descent necessary to initiate a hand catch. RTH was initiated while the throttle was being held at about 10% down throttle in those last down-stick events which apparently caused it to cancel the RTH set altitude and just fly toward home at the current altitude. I see no indication that the AC tried to rise at all once RTH was engaged, meaning that all that was required to cancel the RTH altitude was to be holding a little down stick on the throttle when RTH is first initiated.