A full moon rises above Bartlett Cove, near the park’s headquarters. Four times a day, the moon in this phase will create some of the world’s most extreme tides. In this photo, we see a “minus” tide of a few feet. In other words, the tide has fallen below the “Mean Low Water” level. This happens around new and full moons. In Glacier Bay, the tides can change as much as 24 vertical feet in just over six hours, creating strong ocean currents and exposing a vast array of sub and intertidal marine life. Photographer: Sean Neilson