Greencastle Shore is a sheltered site located south of the old Greencastle pier on the east coast of Ireland. The topography features a transition from sandy patches to rocky outcrops covered in kelp and seaweed. Suitable for beginners, the site reaches depths of up to 12 metres. Divers and snorkellers should be aware of moderate currents, which can occasionally become strong. The water temperature ranges from 8C to 16C throughout the year. Shore access is available, and the site is supported by local facilities including parking, air fills, and equipment rental. Typical dives last approximately 60 minutes.

Greencastle Old Pier is a shore-entry dive site situated at the mouth of Carlingford Lough. The site features old pier structures that function as an artificial reef, offering a vertical reef-like topography. Divers can explore depths ranging from 5 to 25 metres, with an average depth of 10 metres. Conditions are variable, and the site is subject to moderate to strong currents. Due to its sheltered nature, it is suitable for beginners, though caution regarding current strength is advised. The site is also well-regarded for snorkelling.

Haulbowline Lighthouse is a boat-access snorkel site situated at the entrance of Strangford Lough. The stone tower stands on a semi-submerged rock, creating a unique topography for snorkellers. Due to the location at the lough entrance, the site is highly dependent on specific tidal conditions, making it suitable only for advanced snorkellers. Water temperatures in this marine environment range from 8C in the winter months to 16C in August. Snorkellers should be prepared for variable conditions and plan their visits carefully around the tides to ensure safety and visibility at this exposed site.

Cranfield Beach, located at the southernmost tip of County Down, offers a gently sloping shore entry into the marine waters of Strangford Lough. This site features a transition from sandy areas to rocky reef patches and seagrass beds. Snorkelers can expect depths ranging from 1 to 5 metres, with an average depth of 3 metres. The site is suitable for beginners, though visitors should be aware of potential rip currents. Facilities at the beach include parking, toilets, showers, and a cafe. Typical snorkel sessions last around 30 minutes, with water temperatures varying between 8C and 15C throughout the year.

Killowen Point is situated on the northern shore of Carlingford Lough within a Marine Conservation Zone. The site is notable for its rare muddy habitats, which provide an environment for sea pens in relatively shallow water. Snorkellers can access the site from either the shore or by boat. Conditions vary throughout the year, with water temperatures ranging from 8C in March to 15C between July and September. This site is suited for intermediate snorkellers. The habitat supports a variety of temperate marine life, including various invertebrates and fish species typical of the region.

Cranfield Beach offers a shore-entry snorkelling experience at the southernmost tip of Northern Ireland. The site features a mix of sand and shingle, with the eastern end near Cranfield Point providing shallow kelp beds and rock pools suitable for beginners. Water temperatures vary throughout the year, ranging from 8C in March to 15C during the summer months. The habitat supports a variety of temperate marine life, including various reef fish and invertebrates typical of the region. Snorkellers should be aware that conditions can vary, and the site is best suited for those looking for a shallow, accessible coastal environment.

Templetown Beach on the Cooley Peninsula is a sheltered, south-facing site featuring a sandy bay flanked by rocky headlands. This location is suitable for beginners, offering snorkelers access to reef habitats at depths ranging from 2 to 8 metres, with an average depth of 4 metres. Entry is via the shore. Conditions are generally mild, though water temperatures fluctuate between 8C and 16C throughout the year. The rocky areas provide a habitat for a variety of temperate marine life, including various reef fish and invertebrates typical of the Irish coastline.

Hellyhunter Rock is an offshore reef located approximately 2 kilometres southeast of Cranfield Point in Strangford Lough. The site topography consists of a mix of sand, gravel, and large boulders. This is an advanced dive site due to the presence of strong currents, low visibility, and boat traffic. Access to the reef is by boat only. Water temperatures at the site range from 8C in the winter months to 16C in August. While the site supports an algal community, no specific marine life species have been recorded here.