I can't believe you're going to leave us (me, at least) hanging on this one....
Well ok.
Delgada Submarine Canyon - Wikipedia
I tried to look for an underwater map of the typography but couldn’t find it. You just have to use your imagination.
So anyway, back in 2001-02? I was scanning an old US geologic survey map of any radical terrain, canyons, pinnacles, etc. off the Northern California Coast, part of the crazy adventure dives we were into at the time. We wanted to dive places nobody had ever been to.
We stumbled upon the Delgada Canyon and saw that it came right up to shore. So I assembled three other guys and we mounted an expedition.
Mind you, this place is up on the lost coast which is pretty much considered the middle of bum f_ck nowhere. It took 4 hour driving to get up to Shelter Cove then it’s another 8 miles north by boat from there.
We did 4 dives over two days. It took us a bit to find it but we found it. About four hundred feet off the beach we were in 300’ of water. Day one we explored the south side. The water was completely bloomed out. Vis on top was about 3-5 feet. As we went down it cleared up to about 30’ vis but it was black as night. The south side was a very steep mud slope with some rocks jutting out that were covered in white plumose metridium anemones. There were also monster scallops.
The second day was the butt pucker dive. We did the north side this time. Anchored in the mud right at the edge of the drop off. Following the anchor line down it got blacker and blacker until it was pitch black at 60’ where the anchor was. We all had ok lights but not can lights. We compassed down the slope to about 70’ where there was a grouping of rocks all covered with more giant metridiums. We went over the edge of the rocks and realized on the other side it was a sheer drop, Pitch black, no way to reference yourself to anything. Trying to keep track of your buddy by feel and an occasional glimmer of his light, we descended further and further down into the blackness. Situational awareness is very difficult when your light doesn’t light anything because there’s nothing to light up, no bottom. The wall and our instruments were all we had to use as reference. Vis cleared up the deeper we went and we stopped along the wall a few times to regroup and let the adrenaline and nerves calm down. I was pulling reel line the whole time from the anchor so we were not going to get lost. But someplace that remote in pitch black with no practical bottom and an overwhelming feeling about the unknown was freaky. There were several small shelves that stuck out from the wall and every one of them was crawling with spot shrimp. I saw some weird fish on that dive, some deep water fish with lanterns that didn’t belong there.
I think we got about 125’ or so, we were on 32%.
The other two guys went a different way and they were on mix. They actually got pretty close to the bottom but their MOD stopped them. They also reported seeing some pretty weird stuff past 200’.
Later a fisherman we ran into at Shelter Cove told us there are sharks there in abundance. They cruise up the trench and come right up to shore where the trench starts.
People see them all the time, they come right up along side their boats.
The two days we were there the fog was thick, laying right down on the water, and the ocean was glass smooth. This was in September.