Juneau whale watching tours, out where humpbacks feed.

At the dock you walk down a ramp to a small, enclosed boat and settle into a seat by the window. Then the boat pulls out into the channel, the engine settles into a steady hum and everyone starts scanning the water. The first blow usually gets a shout from someone at the back, and from that moment the trip is about watching, waiting and the next surfacing.

When a humpback is near, the captain slows the boat and lets the whale set the pace. You step out on deck, watch the dark back roll through the surface and wait for the tail to rise before a dive. Then it is back inside to warm up, with a snack and a pair of binoculars, until the next whale shows itself.

The scale of the feeding is hard to picture. A single humpback can eat up to 1.5 tons of food a day, mostly krill and small schooling fish. Several whales working the same patch of water can turn a quiet channel into a scene of blows, splashes and diving birds within minutes.

The setting adds to it. The boat runs past forested islands, with snow-capped peaks and, on a clear day, ice fields in the distance. Even between sightings there is a lot to look at, and the light on the water changes from one hour to the next.

The scores back that up. Guests rate the guides at 4.9, the transportation at 4.9 and value for money at 4.7. Comfort comes up often too: the boat size, the warm cabin and the snacks and hot drinks. For a trip on cold northern water, that makes a real difference.

Not every review describes the same day, of course, because no two trips see the same whales. That variety is part of the appeal. Some guests watched bubble-net feeding, others a pod of orcas, others a single humpback close to the boat, and most came back with a story worth telling.

The long northern days help. In mid-June Auke Bay has 17.9 hours of daylight, so there is light for a trip at almost any hour. By September the days are shorter and wetter, but the whales are still feeding before their long journey south.

Outside the season, most humpbacks are far away. They spend the winter in warm waters near Mexico, Hawaii and Japan, although some can be seen in Alaska at any time of year. For a visit with good odds, plan for the summer months.

Orcas are the other great bonus. Travel Juneau lists them among the animals visitors may also see, along with sea lions and porpoises. In Alaska, resident killer whales eat fish, while transients feed on marine mammals.

None of this can be booked in advance. Whales are wild and every trip is different, so treat bubble nets and orcas as gifts rather than promises. What you can count on is a crew that knows the water and the patience to wait for the moment.

The terms are relaxed: hold your seat without paying today, settle the bill later, and drop the booking at no cost as long as it is 24 hours or more before departure. That is useful on a cruise, where port times sometimes shift, and it lets you secure a seat as soon as you know your dates.

Before you book, check the starting times for your day on the listing, since they vary. Then plan the rest of your day around the trip, leaving a comfortable margin if you need to be back on a ship.

Overcast skies, common in Juneau, are kind to wildlife photos. There is less glare on the water and the pattern on a humpback's tail shows clearly. That pattern is how researchers tell whales apart: in Glacier Bay and Icy Strait, scientists identified 237 individual humpbacks in the summer of 2013.

Use the binoculars on board to scan for blows, then switch to your camera when something is close. And now and then put the camera down. The sound of a whale breathing across calm water is something no photo captures.

A waterproof jacket, a fleece or warm sweater and a hat are the essentials. Gloves help in spring and autumn. Choose shoes with good grip, because boarding involves a ramp that can be steep depending on the tide.

Leave bulky bags behind and keep your hands free. A small backpack with a spare battery, a lens cloth and a dry layer is all you need. Snacks and water are provided, so you do not need to bring food.

Binoculars are provided, so you can scan the water for blows and pick out eagles on the shore. A snack bag and water are included too. The guide speaks English and explains what you are seeing as you go.

All boats follow the federal rule against approaching a humpback within 100 yards (91.4 m), with some exceptions. A good crew positions the boat and lets the whales come to it, which is when the best encounters happen.

If you want the Mendenhall Glacier as well, a combo tour can handle both in one booking, or you can visit the glacier on your own after the boat. Our guides to whale and glacier combos and to the rest of Juneau cover both options.

Look around the waterfront too. Sea lions sometimes turn up near the harbors, eagles perch in the tall trees along the shore, and on a clear evening the mountains above town glow long after the boats have come in.

It will not suit every traveler. According to its listing, the trip does not work for wheelchair users, people with mobility impairments or people with back problems, and hotel pickup is not included. If you want a very small group, look at the small-group alternatives in our comparison.

Most of all, come with open expectations. Whales are wild animals, and every trip is different. Dress warmly, keep watching the water and let the channels around Juneau surprise you.