Just a hike along the river Verdon, but few riverside walks feel the pressure of cliffs towering up to 750m. directly above the path. "Keep the river on the right": not a lot of navigation difficulties but a hike which is all about logistics; a couple of nights at the CAF Chalet de la Maline (mountain-refuge style lodging, busy) and avoiding the navette (minibus) reduced these for me. Mind the wet tunnels (torch required) and the vertiginous ladders (burning quads) but otherwise not particularly technical. I enjoyed my picnic lunch on the beach at La Mescla, the confluence of the rivers Verdon and Artuby The great views are in the middle of the hike, climbing over the cliff forming the confluence of the Artuby and the Verdon.
The name Sentier Blanc-Martel commemorates investigations which would have resulted in a hydroelectric power scheme that would have submerged much of this area. World War One diverted attention and happily the scheme was never revived. But the Verdon is no longer a wild river bringing a torrent of melt water down from the Alps: there's a dam at Castillon, upstream of Castellane.