Greetings - I haven't been active in a while, but definitely trying to read up when I can and keep current. I am a single parent of a 9 year old boy, and to be honest following daily started to make me a bit depressed so I stepped back for a bit. Just watching from a distance and not being able to help directly is also a bit frustrating.
I read some questions regarding the water depth and capabilities of divers, and without specific questions, all I can add is some general info. on the limitations of diving and what I think are best procedures based on my experience. All my opinion, coming as a 20+ year dive instructor and former search and rescue diver (a long time ago).
There can be a lot of complicating factors in diving a high altitude lake. Low visibility seems to be the case at Lake V, and underwater trees/snags, uneven terrain, and cold water add to the difficulty. Due to decompression issues, at 8,000 feet elevation, a scuba diver breathing air (vs. other mixtures divers sometimes use), at 60 feet can dive a maximum of 25 minutes. After a surface interval of 4 hours, he could dive again to 40 feet for about 30 minutes (very ballpark figures). So it is limiting, and if the area dived is much deeper than 60-80 feet it would be very difficult to dive and search that depth for any length of time.
Professional recovery dive teams now use ROV's and drop cameras to search areas more safely, and those may be the best option in Lake Vallecito. That being said, if the stories are true that the lake was at 30% capacity last November when the first dive team went in, I suggest that it was a huge opportunity lost to really search the lake with divers. In my opinion, with a child missing, dogs indicating a scent on the lake, and snowfall coming, a much more thorough search should have been done with a much larger dive team (just my opinion, I don't know all the factors involved).
I did just read the newspaper article that showed the police searching the shoreline and building a coffer dam (not too sure why they did that). IMO, a small chain of snorkelers in the water (say 6 or 8), searching parallel to the shoreline could probably cover to a depth of 10 feet, would have been far more effective and thorough. Add 4 scuba divers at a safe depth of 30-40 feet, also swimming parallel to shore just beyond the snorkelers, and a lot of territory could be safely and relatively easily covered.
I would also get the canines out there just before the dive search and see if the area could be narrowed down. Scent dogs are amazing, and they have been known to narrow down search areas significantly, even if a body is deep underwater. If they narrowed it down to even a 100 yard x 50 yard area (about the size of a football field) a very thorough search could be made. It seems odd that they're just searching the shoreline and water down to waist deep. Setting up a snorkeling team or getting one from a neighboring police dive team doesn't seem like it would be that difficult. I'd volunteer myself if it was an option.
Everything is based on what I know if this case, which definitely isn't everything, so I could be off base here. Also, all is my opinion only. I know there are hundreds of professional law enforcement officers, investigators, etc. who sincerely want to help so I don't want to toss unfair criticism their way.
Fingers crossed. While I believe I know the answer to the mystery, my 1% is hanging on for him to escape from a kidnapper and come home safely.