Last weekend, I visited my family in Northern California and we went sailing on one of my favorite bodies of water- Big Lagoon.  We were aboard a 20-foot catboat called Shadow.  Of course, an adventure on the water wouldn't be complete without seeing what things look like beneath the waves, so I brought an OpenROV along for the journey.

Big Lagoon is not known (as far as I'm aware of) to have anything of particular interest in its depths, but then again, that can be said for a lot of places where great discoveries have been made.  

Seasonally, the sand bar separating the lagoon from the ocean breaks open and there have been reports of all sorts of sea creatures that normally belong in the ocean finding their way into the lagoon. In World War II, the lagoon was also used as a bombing target range.

We dove the ROV at several points around the lagoon.  Sadly visibility wasn't very good, and whenever we got to the bottom of the lagoon (about 10m in depth) the view from the ROV's camera would get very dark.  After retrieving the ROV from these dives, we'd find that it had lots of remnants on it of an almost pitch-black silt that had a very noticeable odor.

At one point, we sailed past large log pointing upward with branches coming out of it and wanted to know if it was fixed to the bottom of the lagoon or if it was just floating.  I deployed the ROV and dived down along the log's length, looking at the log with the ROV the whole time, until we reached it's base which turned out to be suspended in the water just a meter or so above the bottom.

Finally, we decided to inspect the boat's propeller with the ROV while the engine was running because there was some debate as to whether the prop completely stopped when the engine was in neutral, or if there was some slip in the transmission as one sometimes sees in outboards which causes the propeller to very slowly spin.  The prop seemed to be completely stopped while in neutral (I lost the bet), but we did also notice that we had been dragging some plant life in the centerboard trunk.

All in all, it was a pleasant trip out on the water with a tool that allowed us to see a part of the lagoon we don't normally get to.  I hope other people around the world with OpenROVs get a chance to experience the same sort of pleasure!

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Comment by Stretch on December 8, 2013 at 3:32pm

@Jim N. - If you want to sample the water at depth, you'll need something like a "Niskin Bottle".  Niskin bottles are a super easy thing to make.  We built them from a section of PVC pipe, 2 rubber plungers and a piece of rubber bungee.  Then all you need is some sort of triggering device.  Here's an article for a DIY Niskin bottle that's a bit more sophisticated than what we used, but should give you some ideas:

http://www.stccmop.org/files/diyniskinbottle.pdf

Comment by Jim N. on December 7, 2013 at 5:15pm

Water sampling device needed. A fellow ROV enthusiast in the valley has a chem lab (he's a chemist) and is anxious to study some samples from our ROVs. I'd love to find out what the black silt is composed of...

Comment by Sam on December 7, 2013 at 3:26pm
Do you think there could have been wreckage from the World War II bombing practice?

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