I think you could be right Kgem about topping the trees.  The pictures of their equipment show that sharc is merely an extendable arm (like on a skytrac or sliding crane boom) attached to a backhoe crawler.  It wouldn't be capable of a depth much more than 30 or 40 feet and that may be stretching it.  Sawfish is submersible and could get to depth, but requires some substantial tethering for it's control cables and even with it's weight (7,700 lbs), size and thrusters, it may not be capable of controlling a 100 foot wooden missile once cut from the base.  

If only topping they are really missing out!  These trees can be 8 feet or more diameter at the base, towering to nearly 100 feet and be about 2 foot diameter near the top.   I would guess that 2/3rds of the tree is still unrecovered in this case and will contain the best, dense and undecomposed portion of timber. 

If they are only going to remove snags and make safer boating 30 feet is cool, but I also read that they are in a bit of a pickle to get the trees out because chemicals released in decomposition are corrosive to components within the hydroelectric dams that created these lakes.

Now, if TigerLynk can get to depth and control the logs safely to the surface.  That's a great opportunity for HIMR.
jmo