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.

Greenore Shore on the East Coast of Ireland is a shore-entry reef site characterised by a silty, cobbled slope. The site is suitable for intermediate divers and snorkellers, though conditions vary. Water temperatures range from 8C in late winter to 16C in August. Divers should be aware of moderate currents, potential low visibility, and local boat traffic. Facilities located nearby include parking, a cafe, and a dive shop. The site offers a practical entry point for those exploring the local marine environment, though users must remain vigilant regarding the changing conditions and maritime activity in the area.

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.

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.

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.

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.

Derryoge Point is a rugged, rocky stretch of coastline located south of Kilkeel. The site features a classic Mourne Coast underwater landscape defined by numerous deep gullies and submerged boulders. Snorkellers can explore these varied rock formations, which provide a habitat for a range of temperate marine life and invertebrates. Access to the water is via the shore. Conditions at this site vary, with water temperatures ranging from 8C to 15C throughout the year. Due to the nature of the terrain and potential conditions, this site is best suited for intermediate snorkellers.