Try the Wrangle Narrows some time between Petersburg and Wrangle in SE AK. When the large ferries transit the narrows it causes a tidal change due to the large displacement of the vessels hull under the water line. As they travel through the tide goes in to the bays and as the ferry passes the tide goes back out into the main channel. Really cool to observe during a day transit of the Narrows. I've done it several times on the AMHS and a few times on my own personal sailboat.
The channel you spoke of between JNU and Sitka is a fun transit. Especially on one of the AMHS's catamaran fast ferries. Flying through the narrow passage at 35-40 mph is a real blast. When the state first aquired the fast ferries I traveled over to Sitka and back on one just for fun. We left JNU and pooped along at 15 knots or so and I thought. "What's the big deal". Well it turns out they were killing time waiting for the tide to come in so the channel was deep enough for us to transit it. They didn't want to waste fuel just to get to the eastern entrance only to sit and wait for the tide to come in from the Pacific Ocean. We stopped in Sitka and the return ride began. Flying north out of Sitka we dodged into the channel and went flying through heading back to JNU. Once through we were passing the usual 100 plus foot yachts with their helicopters on their helipads and we were soon back approaching Auke Bay north of JNU. The USCG came out to meet us and escort us into the Auke Bay ferry terminal but due to sea conditions we left their vessel in our wake as they could not keep up with us at the speed we were traveling at. Made for a fun day trip on a nice day in S.E. Alaska.