The X-Scan, has a grip handle, not a swivel. Swivel handles used for Dowsing are subject to balance, motion of walking, and wind. The X-Scan, is not subject to any of this. It requires motion and can be swept inclined, horizontal, or vertical. You "Feel" It lock when you sweep within inches of a target's emanating field. It is highly directional.
It is impractical to use L-Rods underwater, but I have used them from aircraft, and moving boats.