Shelter Bay Marina is on the far side of the Gatun Locks, and we sometimes had to wait for the shipping traffic before we could pass. On one of our last trips to Shelter Bay in the rental car, we took advantage of the wait to visit the Gatun Locks observation deck and watch the ships up-lock.
Although we had already been in the locks, this perspective is awesome. It's the closest we've been—or ever want to be—to a container ship.