Question 4332
If the lure dropped to 22 ft. below the surface and was taken down an additional 15 ft. then it is now at (22+15=37) 37 ft. below the the surface.

Next, James reeled the lure and trout straight up for 30 ft. so it is now (37-30=7) 7 ft. below the surface.  At which point the line snapped and the big one got away.
So the fish was at a depth of 7 ft. below the surface.