This hydrophone is located off of Dearth Island, about 15 kilometres from Bella Bella, listening below the surface in Seaforth and Spiller Channels. Seaforth Channel is part of the Inside Passage, and many travelling tugs, ferries, and fishing boats pass by here. To the west lies one of the main access points to the Inside Passage, Milbanke Sound, which is exposed to the open Pacific Ocean. Whales frequently use this channel to travel between the inner and outer coastal waters. Resident killer whales are heard here during the summer, and Bigg’s (transient) killer whales can be heard throughout the year.