July 4, 2008 was a beautiful North Coast day with almost no wind, just lightly overcast, and minimal swell. Curt Billings and I met Eric Sedletzky at the Arena Cove pier to dive Arena Rock on Eric’s custom boat. We put on our wet suits on in the parking lot, and loaded out gear into the boat before Eric pulled up to the lift.

Eric’s boat is a custom built 18’ wood vessel that Eric built from scratch specifically for North Coast diving. He used plans for the hull, and all other additions are his design. His additions to the basic design include the raised floor with separate stowage lockers for several divers, the center console, the anchor chain locker/seat in the bow, the stainless steel tank rack in front of the center console, and a strap system tailored for the Arena Cove lift. The boat drafts only a few inches so it is ideal for beach launching and can make it over the shallow sand bars in river mouths such as the Albion River. He also built the custom trailer with an extendable tongue to ease beach launching. Although Eric is very modest about it, I must say it is the nicest small boat I have ever had the privilege of diving from.

Once the boat was in the water, and Eric had parked his truck we headed for Arena Rock.
Arena Cove where we launch is just SE of Point Arena. Arena Rock is about one mile north of Point Arena. Eric has been there enough that he uses landmarks line-up to navigate. He has a GPS, but did not turn it on.

Eric anchored on the down current side of the rock. On the first dive Eric and I went down while Curt remained behind on the boat. The surface water temperature was 48°F. Eric and I followed the anchor line down. At 105’ there was a very brisk thermocline. As soon as I went through it my face stung and I had an instant ice cream headache. My computer read 45°F and was still falling when I popped back up to 100’ above the cold. At that level my computer’s temperature reading stabilized at 46°F.

The rock itself has a fairly steep face with many deep shelves and caves. It is very exposed and gets well fed so the invertebrate life on it is very lush. There were many very large nudibranchs. It also had many large clusters of Gersemia rubiformis (Sea Strawberry Soft Coral) which I had only seen in books before. Aberrantly it is common in Washington, Vancouver, and Alaska. There were also many large Orange Sea Cucumbers (Cucumaria miniata) which I had not seen before. Some of the invertebrates I had seen at San Miguel and San Nicolas Islands, but they were much larger and denser here. There were also large patches of Distaplia smithi (Paddle Ascidian). Back under the shelves and in the caves there were many Rock Scallops (Crassedoma giganteum) which Eric spent his dive getting.

Once Eric and I returned to the boat Curt took a turn diving. While he was down I took some pictures of the view while anchored at the rock. Once Curt returned Eric and I made a second dive. On that dive I saw the biggest rockfish I had ever seen, I guestimate it was about 25 lbs. Luckily I managed to get one picture before it dashed away from me. I thought is was a Vermillion, but it turned be a Yelloweye Rockfish (Sebastes ruberrimus).

Once Eric and I returned we headed back to Arena Cove. However we went in close to Point Arena so Eric could meter some of the many reefs that extend out from the point.

I was a wonderful dive I would love to do again. I can’t thank Eric enough for taking us there. I have many pictures from the trip. Click on the link below to see them.

©2008 Chris Grossman, diver.net

• Underwater Photographs from Arena Rock, Mendocino County, California

• Re: Belated Dive Report: Arena Rock with Eric Sedletzky Merry 08:27:40 08/01/08 (0)
• Re: Belated Dive Report: Arena Rock with Eric Sedletzky Eric S 19:07:24 07/31/08 (0)
• Re: Belated Dive Report: Arena Rock with Eric Sedletzky Patrick 10:09:25 07/31/08 (1)
  • Re: Re: Belated Dive Report: Arena Rock with Eric Sedletzky PB 21:06:12 06/11/09 (0)
• Extremely cool ... uh.... brrrrrrrr!!! seahunt 06:05:27 07/31/08 (0)