100 feet is certainly believable. It's not at all unusual in Western super clear lakes. We have divers inspect the dam and they use cameras where the depth is too great for scuba diving. They've taken videos of LMBs at least down to 130' at the intake to the powerhouse, and they are monsters. Nobody catches those that anyone knows about. We believe there are at least a dozen new state records there. They've found 60# plus stripers there too.
Catching one from more than about 40 feet down is likely to cause the air bladder to inflate. The best tactic is to use a weighted line run through the lower lip, releasing them back at the depth caught. You need twice as much line as that depth. When it reaches the target release the end of the line opposite the sinker (1/4# weight) and reel the weighted end up. You should feel the bass get very active when it gets back home.
During passage of a cold front or storm they normally only drop a few feet, not swimming way out to deep water.
Jim