Just my opinion & speculation, but I've been to Silver Glen many times (non diving) and it has a strong flow even in the channel out to the lake. Back in the 1990's it was a huge weekend party place with hundreds of boats parked & lined up on both sides of the channel. Now all that has been shut down and it's very quiet there during the week days.The water in the channel is so clear, you can read a newspaper headline on the bottom, so he would be easily spotted. It would be very easy for a non-buddy-diver with SWB to be carried by the flow out towards Lk George and no one notice at all. Once outside the channel in the lake there is not much population right next to the shoreline on both lake sides of the channel. It's a huge no vis lake, and with currents and wind, he could be anywhere on it to search and get him back. Again, just my own opinion from frequent visits there several years ago.