~100' is the deepest for me and it was something that we did intentionally on a calm night. When I worked commercially, we would regular anchor in Sommes Sound, ME in about 60-70' of water and outside of the mooring field in Isles of Shoals in about 50-70'. We anchored in Castine, ME once in a little over 80' of water to quickly run ashore. It was a rare night when we didn't have at least 30' of water under us at high tide.
The S/V Westward anchored on Stellwagen Bank two summers ago overnight. They said the noise of the whales made it difficult to sleep.