Castel Bay is a coastal bay on Banks Island within Aulavik National Park in the Inuvialuit Settlement Region. It is a remote, high-Arctic saltwater feature located on the south side of M'Clure Strait. The bay is a designated aircraft landing area within the park, providing a primary access point for paddlers arriving by air charter. The Thomsen River, a notable paddling river within the park, flows into Castel Bay, and the lower river and bay area form a significant bird sanctuary established in 1961. This area is a concentration point for moulting birds, particularly Brant geese, with numbers that can reach up to 5,000. The mouth of Castel Bay is characterized by a sand or gravel bar. The surrounding waters are brackish, and the area is known for fish species like the Fourhorn Sculpin. Paddling in this region is typically conducted via canoe, with survey work historically occurring between June and August. The experience is defined by extreme remoteness within a national park setting, requiring careful logistical planning and adherence to park regulations. There are no developed facilities, amenities, or specific water temperature data for paddlers. The primary considerations for trip planning involve coordinating air access to the designated landing area, understanding the protected status of the bird sanctuary, and preparing for a wilderness expedition in a fragile Arctic environment.