We have 300 feet of line and 30 feet of chain. We've anchored in just over 40 feet, and I wouldn't want to go much deeper. Even with a manual windlass, I still get a great upper body workout at that depth.
Theoretically, with that much rode and chain, we could anchor in 100 feet at 3:1 scope. However, as Faster and others have suggested, you then have to get it back on board.
As for diving? We live on Canada's west coast. Diving is a great way to get hypothermia!