Not Your Everyday Dive Site

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Posted by Merry on September 08, 2016 at 12:37:45:

The Hurst Isle spun slowly in the eddy as Captain Bill Weeks gave the dive briefing. No one on the boat seemed surprised that we were rotating 360 degrees, but I could swear I could hear a few hearts pounding. “At the right time, I’m going to drop you at this notch in the rock. Wait there until I tell you, then all of you drop together,” said Bill. Descending ~20 minutes before slack tide, we were advised to hang out a little until the tide started to turn. Then stay within a calm triangle that would form between two opposing currents, created as the flood was ending and the ebb was beginning. “Push forward until you bump up against it, then drop back. When you feel it bump from the back, move forward.” During the narrow window of dive opportunity of approximately 40 min., the triangle would move along the rock and carry us around to the end. “Keep the rock to your right, and don’t go below 40 feet or you’ll be swept away into the channel and who-knows-where you’ll end up.”

We were about to dive the infamous Nakwakto Rapids at Turret Rock, aka Tremble Island, just off the mainland of British Columbia. The tiny island, not much more than a rocky pinnacle, sits in the middle of a narrow channel, forming a bottleneck through which pass the tidal exchanges for Seymour and Belize Inlets.

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Tremble Island
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Nakwakto Rapids is listed in the Guinness Book of World Records as having the fastest navigable tidal rapids in the world. The rapids can run up to 16-20 knots on a maximum ebb current. Several conditions, the weather, time of day, and minimal tidal range at slack tide, must coincide in order to dive the site. Based on these parameters, there are only 3 diveable days in 2016!

The Nakwakto Rapids current table predicted slack tide at 11:52 a.m. After that, it started to get gnarly quickly.

2016-08-12 Fri 2:05 AM PDT -7.5 knots Max Ebb
2016-08-12 Fri 6:12 AM PDT Sunrise
2016-08-12 Fri 6:24 AM PDT 0.0 knots Slack, Flood Begins
2016-08-12 Fri 9:41 AM PDT 4.3 knots Max Flood
2016-08-12 Fri 11:52 AM PDT -0.0 knots Slack, Ebb Begins
2016-08-12 Fri 2:16 PM PDT -4.7 knots Max Ebb
2016-08-12 Fri 5:18 PM PDT 0.0 knots Slack, Flood Begins
2016-08-12 Fri 7:57 PM PDT 6.8 knots Max Flood
2016-08-12 Fri 8:55 PM PDT Sunset
2016-08-12 Fri 11:37 PM PDT -0.0 knots Slack, Ebb Begins

The highly sought after subject at this site was Pollicipes polymerus, the red gooseneck barnacle.
At ~8-inches, it's the largest species of barnacle. As we first made our way through cuts in the rock, we encountered solid masses of the 10-inch long Vancouver feather-duster worm, Eudistylia vancouveri. Their parchment tubes were often covered with yellow sponge.

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The worms also provide a scaffold for the proliferating anemone, Epiactis prolifera

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Beyond the feather duster worms lay an incredible sight, mass upon mass of red-tipped, gooseneck barnacles. Solid beds of large, tightly packed barnacles covered the sides of the rock, creating their own seascape, thriving in a spot one would think should be scoured of all life.

Their red color is due to hemoglobin in the barnacle’s blood. Goosenecks at this site don't develop the protective pigment found in goosenecks that are more exposed to the sun.

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Red goosenecks grow mixed with the mussel, Mytilus californianus
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There were many beautiful anemones at the site, but I was transfixed on the barnacles.

Painted anemone, Urticina grebelnyi
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Our next dive there will be in August, 2018.

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