- The Swinomish Channel is an 11-mile (18 km) long salt-water channel in Washington state, United States, which connects Skagit Bay to the south and Padilla Bay to the north, separating Fidalgo Island from mainland Skagit County. The Swinomish Channel is the smallest of the three entrances to Puget Sound�the other two being Deception Pass and Admiralty Inlet.