Even after scrubbing, those surfaces were still covered with hard deposits. I wonder if hydrophobic paint would prevent this?
With the the dive deployments done, and the Rio Secreto installation out of the way, it was time to start wrapping up the trip. Sometimes we are forced to leave the open water flow units with Gabriel at C.E.A., but he had important meetings that morning and I had enough time on to install them on my own. As we talked about potential sites for other units, I laid out the loggers, cables etc. on the table. He was somewhat surprised to see the condition of the older units.
Nothing like a good hydrochloric acid bath at the end of a long deployment.
You see when we retrieved B3 & B4 at the start of the trip, months in the sea had coated them with so much bio-growth that they looked like something from “Pirates of the Caribbean”. On previous trips, hard scrubbing and bad language were enough to sort them out, but after that failed I knew we were going to need bigger guns. After googling my way through a few chemical resistance charts, we popped down to the hardware store for a bucket, and bottle of muriatic acid. And as we hoped it was highly effective, but I was biting my nails as we watched the loggers, and the data they still contained, fizzing away like seltzer tablets. Fortunately those EPDM O-rings held up, and after a few hours in the soup, I was finally able to scrub away the crud and get to our data. I did my best to keep the sensor wells away from the acid, as the epoxy there was already getting pretty old.
So by the time I was ready to swim out into the bay, our flow sensors had gone through something of transformation:
B4 before & B4 after
I spent a fair bit of time locking down a new anchor plate for B3, with sea urchins and rolling surf conspiring to make that a challenge. And I don’t know if it was the fact that I was further out on the reef, or that I just did not move like the tourists, but I swear critters came of the woodwork just to see what I was doing. The barracudas were probably drawn in by the shiny metal surfaces on the camera, and at one point, while I was busy looking down to capture some clips of B4 in motion, a sea turtle swam right into me. I know it sounds funny, but an impact from something that big when you are floating in the sea can really scare the willies out of you. When I spun round to see what happened, there were three more beside me (…probably doing the turtle equivalent of laughing…inside…) But by this time the loggers were installed, and I was too worn out from all the swimming to spend any time watching them. Reluctantly, I headed back in.
Of course, things always happen when you are not looking for it, and as I made my way to shore I noticed a spotted eagle ray swimming nearby. I was in the boating lane at the time, and decided that trying to capture a photo was not worth getting run over, so I just kept going. However, once I reached the shallower sandy area, he reappeared right under me, and this time I dug the camera out of the mesh bag I had been using to ferry the loggers around:
…and I think I will use that to sign off on a brilliant fieldwork trip.
Addendum
By the end of all this, my field-notes went over 50 point-form pages of observations, readings, etc., and there is no way I could relate more than a small sampling of that here. Once the major diving is done, we try to grab a little social time with friends as we drop off various bins of gear to be stowed till next time. Trips like this could never happen without the help of the dive community in Tulum, and we are grateful for all the help they have given us over the years. Of course a proper list of thank-yous would be even longer than my field notes, but I’d like to give a special shout out to Bil, Robbie, Kim, Natalie, Jeff and Gosha. I hope some of this blog-y catharsis makes you laugh, and some of it makes you proud, because you are all an important part of it.
Cheers!
Underwater Arduino Data Loggers 