As its name implies, much of Glacier Bay National Park is water. Most of the land within the park is mountainous, covered with dense rain forest or alder thickets, and without roads or trails. While a few hardy travelers hike, raft, or climb the mountains, the vast majority of visitors travel by salt water. Glacier Bay is a natural waterway from Alaska's Inside Passage to the tidewater glaciers that are the park's main attraction. Its numerous branches, inlets, lagoons, islands, and passages offer virtually limitless opportunities for exploration.

Most visitors to Glacier Bay see the park from large cruise ships with thousands of passengers. These visitors do not go ashore in the park; instead National Park Service naturalists board the ship to share their knowledge about the park and its wildlife during a day-long cruise in the bay.