A Glacier Bay day is worth understanding as its own part of an Alaska itinerary. I'd set aside room for the scenery and the ranger program, then resist filling every gap with something else. The essential planning questions are whether the sailing includes the park, how a cruise-ship visit works, and how to watch without expecting wildlife to come closer. Those details help you decide what the day should mean for your trip.
The National Park Service's cruise-ship information says ships do not dock anywhere in Glacier Bay National Park. A typical visit lasts a full day, about 9–10 hours, and includes a stop at a major tidewater glacier. Think of this as time spent experiencing the park from aboard, rather than a port day built around walking off the ship.
NPS says a park map is delivered to the stateroom the evening before arrival. I'd use that map to orient yourself before the visit and keep it handy as a reference during the day. Let the route and the narration guide your attention instead of trying to turn every moment into a photograph. Leave some unstructured time to look, listen, and understand the place you're passing through.
The park's vessel-management account says a permit system has regulated the number of entries into the bay since 1985. It covers cruise ships, tour boats, charter boats, and private boats. Vessel traffic is managed under a November 2003 decision based on that year's Vessel Quotas and Operating Requirements Environmental Impact Statement.
Glacier Bay National Park and Preserve comprises 3.3 million acres, including 940 square miles of marine waters. NPS describes traffic management as a way to protect natural and cultural resources while providing a range of visitor experiences and encouraging understanding. The size of the park does not make ship access unlimited; the permit system is part of how a visit works.
I'd keep the practical conclusion simple when comparing itineraries: identify a Glacier Bay visit explicitly. Neither the scale of the park nor the general promise of an Alaska cruise answers whether your particular sailing goes there.
NPS rangers board cruise ships to narrate important aspects of the visit, give special presentations, offer Junior Ranger activities, and staff an information desk. That gives the day several ways to learn about the park alongside the views. My advice is to make room for a presentation and bring your questions to the information desk.
If you're traveling with children, consider how the Junior Ranger activities could fit with watching the scenery together. You don't need to turn the entire day into a timetable. Choose the parts of the ranger program that interest your group and leave enough breathing room to follow what catches your attention outside.
NOAA Fisheries' Alaska viewing guidance separates regulations from voluntary recommendations. The Alaska humpback approach regulation, in effect since July 2001, prohibits approaching within 100 yards. It also prohibits putting a vessel in the path of an oncoming humpback so that it surfaces within that distance, or disrupting the whale's normal behavior. Vessels must operate at a slow, safe speed near humpbacks.
NOAA's general code recommends remaining at least 100 yards from marine mammals and limiting observation of individuals to 30 minutes. Its voluntary harbor-seal guidelines in glacial fjords recommend 500 yards where safe navigation permits, avoiding wakes and abrupt changes in course or engine pitch, and avoiding loud noises. I'd bring binoculars and judge a sighting by what you can observe from a respectful distance.
Additional voluntary measures apply in Disenchantment Bay near Hubbard Glacier and Tracy Arm from May 15 through June 30. Keep those place-specific notes attached to those places when considering other Alaska outings. NOAA also describes Whale SENSE as a voluntary program operating since 2015 in the Juneau whale-watch community, recognizing commitments that include reduced speeds and time limits around whales.
NPS cautions that many Alaska cruise offerings do not visit Glacier Bay National Park. I'd read the day-by-day route and look for the park by name, then decide how much that visit matters to your choice. A broad destination label is less useful than the actual itinerary for answering that question.
The Alaska cruise guide puts Glacier Bay alongside the other route and port decisions. Keep your comparison focused on the experiences you want, with the park visit treated as a specific item to identify rather than an assumption about every Alaska sailing.