I spoke to the crew last night. They are a good bunch from Florida who was enjoying NY hospitality. They are indeed using a type of sonar that requires those small pressurized air explosions to get their readings of the salt mines. The release of pressurized air is about 2-3 foot under the surface. The sonar cable is 2500' long and is only about 3' under the surface. They have been completely cut off from their cable on a couple occasions by boat props (Not on our lake). They admit to not having the proper signaling flag. The reason being their hired tow company that towed their vessel from Florida broke them off on a bridge on the way up. They also admit they should fix it. They have been approached by the DEC, Marine Safety and Sheriff because at the end of their cable is a empty row boat of some type. People saw a empty boat and called the police. I showed them this thread and they were impressed by how much more people on this thread knew about what they were doing then they did.