Sea level is not the same in all places – but what if the places are only 10 feet apart?

I’m at Deception Pass, at the north end of Whidbey Island. In the middle of the pass is a small island, and at the eastern tip of that island is a point where the water level falls away into a hole. I just don’t get what’s going on here and I haven’t been able to find any information.

I can accept that sea level is not the same in all places – tides, the moon’s gravitational pull, continents in the way, these sorts of things can cause differing sea levels – but this difference within such a small distance boggles my mind. I need some oceanographer, geologist or alchemist to explain what I’m seeing.

First attempt at posting video, which I don’t even try to shoot very often, so please forgive the quality. I’m also not used to speaking instead of writing so I stumble all over my words. But enough disclaimers. I just thought I’d put this up and see if someone knowledgeable can give me an explanation.

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Ranger Rick Blank of Deception Pass State Park gave me his idea of what’s going on: the channel in the Pass being so narrow all the water trying to get through stacks up behind Pass Island. I can see that, the island acts like a half open lock gate. I’m not sure that accounts for this hole though. Underwater channel or canyon, reef at the east end of the island? Or am I all amazed over something perfectly normal and trivial?

Whatever the case, this guy knows what to do with the situation.