The locks here do 3 things:
1. maintain the water level of the fresh water Lake Washington and Lake Union at 20–22 feet above sea level.
2. prevent the mixing of sea water from Puget Sound with the fresh water of the lakes.
3. move boats from the water level of the lakes to the water level of Puget Sound, and vice versa.
We saw the locks in operation so that several ships could move through one way or another.
We also viewed the Fish Ladder. Unfortunately, it was still a bit too early for the salmon - "peak" viewing time is during spawning season, from about the beginning of July through mid-August.
The grounds also features a visitors center, which is closed on Tuesdays, as well as the Carl S. English, Jr., Botanical Gardens.