Ísafjarðardjúp, the 75-kilometer fjord cutting into Iceland's northwest shoulder, holds the country's densest summer concentration of humpback whales—nineteen catalogued individuals returned to these waters in 2025, their fluke patterns mapped by the Icelandic Marine Research Institute. The fjord's bathymetry creates a natural feeding corridor: cold Arctic water collides with warmer Atlantic currents along a submerged shelf 400 meters deep, stirring nutrients that fuel krill blooms dense enough to support 30-ton cetaceans from May through September. Shore-based whale watching infrastructure arrived in Ísafjörður only in 2003, nearly two decades after Húsavík claimed Iceland's whale-watching crown, but the town's late entry preserved a less commercialized approach—small-capacity RIBs and converted fishing boats rather than triple-deck tourist vessels. Ísafjörður's whale watching tours launch from the working harbor at Aðalstræti, where century-old herring-salting warehouses now house booking offices and maritime outfitters. The departure point sits beneath Eyrarfjall, a 731-meter massif that shadows the waterfront until mid-morning in winter and creates microclimatic wind patterns operators read before choosing routes into the fjord system. Humpbacks dominate sightings—breaching, tail-slapping, and bubble-net feeding recorded on 73 percent of summer departures—but minke whales, white-beaked dolphins, and harbor porpoises appear frequently enough that operators list them as secondary targets rather than incidental bonuses. The Ísafjörður whale watching tour season technically runs year-round, though December and January departures occur only when sea ice remains offshore and wind speeds drop below 12 meters per second. The Westfjords marine expeditions differ from south-coast whale tours in duration and encounter probability. Ísafjarðardjúp's sheltered inner reaches lie 20 to 40 minutes from the harbor, and the fjord's branching arms—Hestfjörður, Skutulsfjörður, Álftafjörður—offer fallback routes when wind closes the outer waters. Tour operators coordinate sighting reports by VHF radio, a cooperative practice inherited from the region's fishing fleet and formalized through the Westfjords Cetacean Network in 2018. The network's real-time data sharing has pushed encounter rates above 85 percent in summer months, a figure that includes all cetacean species rather than humpbacks alone. Guides aboard Ísafjörður departures draw disproportionately from the town's 2,600 residents, many with multigenerational fishing knowledge that translates into nuanced route decisions and an unsentimental interpretation of animal behavior—whales as wild, migratory, and subject to their own rhythms rather than performing spectacles.