The Churchill River Estuary in Canada is a unique site where the river meets Hudson Bay. This location is primarily accessed by boat, which is required due to the nature of the environment. Snorkellers should be prepared for challenging conditions, including strong currents, low visibility, and very cold water temperatures that range from -1°C to 10°C throughout the year. A thick wetsuit or drysuit is essential for safety in these temperatures. The site is rated for intermediate snorkellers, and typical sessions last up to 120 minutes. Hazards at this site include boat traffic, cold water, low visibility, and strong currents.

Sloop Cove is a sheltered location on the west bank of the river, historically utilised by the Hudson's Bay Company. It offers a calmer environment for snorkelling compared to the main estuary. Access to the site is by boat, located 3200 metres from the shore. Conditions are characterised by mild currents and low visibility, typically ranging between 1 and 5 metres. The water is extremely cold, with temperatures fluctuating between -1°C and 10°C throughout the year. Wetsuits are essential for all in-water activities. The site is suitable for beginners, though users should remain aware of boat traffic and the challenging cold water conditions.

Button Bay is a reef site located northwest of the main river mouth near Churchill, Canada. It is distinguished by visibility that is generally superior to the nearby estuary. Divers access this site by boat, and it is suited for advanced divers due to the challenging conditions. The environment is characterised by moderate currents and extremely cold water temperatures, which range from -2C to 8C throughout the year. The site supports a variety of regional marine life, including various reef fish and invertebrates typical of this cold-water habitat. Hazards include low visibility, strong currents, and the risks associated with extreme cold water.

Mosquito Point is a shallow section of the Churchill River estuary in Canada. This site is accessed exclusively by boat and is suitable for beginners. The environment is characterised by low visibility due to high levels of silt and tannic acid in the water. Conditions are challenging, with hazards including boat traffic, surf, and extremely cold water temperatures that typically range from near freezing to 10C. While the site is a known congregation area for belugas, no specific marine life can be confirmed for this location. Snorkelling sessions here typically last up to 120 minutes.

Located 45km north of Churchill, the Seal River Estuary is a remote marine site accessible only by boat. This advanced-level site requires specialised expeditions to navigate the environment. Divers and snorkellers encounter extremely cold water temperatures, which typically range from -2C to 10C throughout the year. Conditions include moderate currents and visibility that can reach up to 15m. Due to the challenging nature of the site, including low visibility and strong currents, it is suited for experienced divers. Boat traffic is a known hazard in the area. Guided tours are available to facilitate access to this remote location.