West Seattle Trench

Date Reviewed:July, 2002
Location:Just past the lighthouse on Alkik
Access:Shore Dive
Site Description:Very steep slope down into the Sound
Main Attraction:Very easy to get deep fast

I've only been diving at the Trench once, with a friend who was doing a Trimix class, and needed someone to accompany him on his deep dives. And deep we got, around 160 or so, without swimming too far out.

To get to the dive location, drive past the lighthouse on Alki (headed south), until you come to a stop sign. At the stop sign, turn right, and drive about 300 yards until you see a tiny one or two lot wide park. There is a little bench there that looks over a tiny little slope down to a cobblestone beach. The little park may have a name, but I don't know what it is. Park on the street preceding the park, and gear up. The hike down to the beach is a little treacherous (although nothing is as treacherous as Sunrise. Wind your way through the tall grass, over the driftwood, and down the cobblestones to the water, and breathe a sigh of relief as you finally can take the weight off your aching back and legs.

As you swim out on the surface, looking back toward the beach, you'll notice that there are two bulkhead walls located on either side of the cobblestone beach from which you entered the water. Line yourself up with the wall that is on your right (to the south), and swim out about 100 yards or so (at medium to low tide), take a bearing on the beach, and descend.

Once on the bottom, swim west, and slightly north to find where the trench begins. It's not a huge dramatic crevasse, but the slope of the bottom does change drastically; you'll know when you've found the edge. The bottom here is silty muck like most of the puget sound, but I did see some of the biggest Sturgeon Poacher I've ever seen (narcosis? Probably). We also encountered a good sized Red Octopus at about 145 feet, out hunting.

The visibility was terrible, about 10 feet, all the way down past 100 feet, with big snotty chunks in the water. This might have affected my impression of the site, so I'll probably try it again in the winter, or when the visibility is better. Who knows, maybe the trench is impressive if you can actually see it begin!

As you come back up the slope, watch for all sorts of bottomfish (flounder, sanddabs), Red Rock Crab, Graceful Crab, Red Octopus, and other common Puget Sound denizens. Also up top while doing safety stops in the shallows, look in the extensive eel grass beds for all sorts of neat stuff.

Be careful when you dive here, as it is obviously very, very easy to get really really deep. We had a planned depth and time limit, and then decompression stops all the way back up the slope. I used my buddies stage bottle, which was filled with 40% for most of the return trip and deco stops. It's possible to do this as a non-decompression dive, but pick your nitrox mix and bottom time carefully.

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