The Tacoma Narrows are an amazing place. When you think of the huge quantity of water that has to move into and out of the entire South Sound, twice a day... all that water has to get there via the Narrows. Its no wonder that the tidal currents here are prodigious. Because the Narrows are after all, well... narrow.
This chart segment (depths in fathoms) shows that The Narrows are just South of Gig Harbor, and almost appear to be an extension of Colvos Passage, which extends to the North in the center of the chart segment. Depths are not a concern.
Tidal current, however, is. Unless it is a small tidal change, or unless you have a very large engine, you will not attempt to stem the tide here. But despite the magnitude of the current, there is very little turbulence (not at all like Deception Pass!) Transiting The Narrows is more like boating on a mile-wide river.
If you watch the locals, they will show you how to take maximum advantage of the higher speed flows within the general tidal current. Like canoeists in a river know, the maximum flow will always be at the outside of the bends in the river channel. So too for The Narrows. Our maximum speed-over-ground (as shown by GPS) so far is 13 kt in The Narrows... What's yours?
You will get to see the magnificent Tacoma Narrows Bridge from a unique perspective: sea level. Don't worry about clearance above your mast - there is plenty of room. Oh, and these pictures were taken in 2002 - before construction of the second span (that is, an entirely new bridge, right next to the old one).
I should point out that The Narrows funnels air flow as well as water flow. When the wind is up, it will really be up in The Narrows. For entertainment, check out some links to the first Tacoma Narrows bridge in the wind - an interesting study in resonance. Can you imagine the entire bridge span vibrating like a bowed violin string? It only lasted 4 months.