Skerries Cavern is a shallow cavern and reef system located on the shoreward side of the Skerries islands in Strangford Lough. The site features walls encrusted with sponges and soft corals. With depths ranging from 5 to 15 metres and an average of 10 metres, it is suitable for intermediate divers and confident snorkellers. Access is by boat, as the site is situated 4000 metres from the shore. Conditions vary, with visibility between 3 and 25 metres and moderate currents. Water temperatures fluctuate between 8C and 15C, so a good wetsuit is recommended. Divers should be aware of sharp coral present within the cavern environment.

Ramore Head is a boulder slope site situated 700 metres offshore from Portrush. The seabed features a mix of kelp forests and red algae, creating a varied underwater topography. Depths range from 8 to 30 metres, with an average of 23 metres. Conditions are variable, with moderate currents and visibility typically between 5 and 10 metres. Access is possible via both shore and boat, though the site is best suited for intermediate divers due to potential hazards including boat traffic, entanglement risks, strong currents, and surf. Facilities available in the area include parking, toilets, boat charters, and guided tours.

Lansdowne, known as The Arcadia, is a shore entry snorkel site located in Strangford Lough. The area features a rocky shoreline and shallow reefs that are sheltered from western winds. These conditions provide a relatively accessible environment for beginners to explore the intertidal marine life and kelp fringes found along the coast. Water temperatures at this site vary between 8C and 15C throughout the year. With a snorkel rating of 3/5, it offers a manageable experience for those looking to observe the local coastal environment in a sheltered setting.

The Skerries is a chain of islands in Strangford Lough featuring a diverse underwater topography of bedrock reefs, kelp forests, caves, and drop-offs. The northern face is characterised by rugged terrain with deep fissures. Depths range from 1 to 30 metres, with an average of 12 metres. Access is by boat only, and the site is suited for advanced divers due to moderate currents and potential hazards including entanglement and surf. Visibility varies between 5 and 20 metres. Species recorded around this area include grey seals, harbour seals, catsharks, various crab species, and tube worms. The site is also suitable for snorkelling.

Blue Pool in Portrush is a natural rock pool and inlet characterised by dramatic underwater gullies. The site features a shallow cave and several rocky overhangs that provide shelter for marine life. With water temperatures ranging from 8C to 15C throughout the year, this shore-entry site is suitable for beginners. It offers a snorkel rating of 4 out of 5, providing an accessible environment for those looking to explore the coastal topography near Coleraine. Divers and snorkellers should be prepared for variable conditions typical of the Northern Ireland coastline.

Whiterocks Caves in Strangford Lough features a series of limestone sea caves and arches carved into white chalk cliffs. The site includes distinct formations such as the Wishing Arch and Elephant Rock, where the white chalk seabed creates high-contrast conditions. Depths range from 0 to 10 metres with an average of 5 metres. Access is available via both shore and boat. Divers and snorkellers should be aware of moderate currents, surf, and potential rip currents, alongside the overhead environment of the caves. Water temperatures fluctuate between 8C and 15C throughout the year. Facilities at the site include parking, toilets, and showers.

Mermaid's Cave is a sea cave situated directly beneath the ruins of Dunluce Castle. The site features a cavern reaching 60 feet in height and an adjacent limestone reef. Snorkellers can access the site from either the shore or by boat. Water temperatures at this location vary between 8C and 15C throughout the year. Due to the nature of the cave environment and local conditions, this site is best suited for intermediate snorkellers. The area is rated 4 out of 5 for snorkelling activities.

The Herring Pond is a natural deep-water rock pool in Strangford Lough, protected by an artificial breakwater that maintains calm conditions even when the nearby Atlantic is choppy. This site is suitable for beginners and offers a shallow environment reaching depths of up to 6 metres. Snorkellers can observe dense kelp and thongweed ecosystems. Marine life recorded here includes snails, which are very common, alongside uncommon sightings of catsharks, rock crabs, tube worms, and European green crabs. Rarer encounters include skates, giant jellyfish, various crabs, rockpool prawns, and shannies. The water remains cold throughout the year, so a 5mm wetsuit with gloves and boots is recommended for comfort. Entry is via the shore.