Dorothea Quarry is a flooded slate quarry in Mid Wales, recognised as one of the deepest accessible freshwater dive sites in the United Kingdom. The site features steep quarry walls, submerged machinery, and industrial debris, creating a complex overhead environment. Depths range from 3 to 104 metres, with an average of 40 metres. Visibility is typically between 10 and 30 metres. Due to the significant thermocline, water temperatures drop from 16°C in the shallows to 4°C at depth. This site is suitable only for advanced, deep, or technical divers. Shore entry is required, and a drysuit with an appropriate undersuit is strongly recommended due to the cold water conditions.

Trefor Pier is an artificial reef site located in Pembrokeshire, United Kingdom. Divers can explore the structure at depths ranging from 2 to 8 metres, with an average depth of 6 metres. This shore entry site is suitable for beginners and offers mild currents. Visibility typically ranges between 5 and 10 metres. The site is accessible for night diving, with a typical dive duration of 60 minutes. Facilities available at the location include parking, toilets, air fills, and a cafe. Divers should remain aware of potential hazards, including boat traffic, entanglement risks, and surf conditions. Water temperatures fluctuate between 8C and 17C throughout the year.

Porthdinllaen is a sheltered bay in Pembrokeshire, United Kingdom, defined by its extensive seagrass meadows and reef topography. This site is suitable for beginners, offering shallow dives with an average depth of 3 metres and a maximum of 5 metres. Shore entry is standard, with mild currents and visibility ranging from 3 to 10 metres. The habitat supports a variety of temperate marine life, including various reef fish and invertebrates. Divers should be aware of potential hazards such as boat traffic, jellyfish, sea urchins, and surf. Facilities including toilets and a cafe are available nearby. The site is also suitable for snorkelling and night diving.

Vivian Quarry is a flooded slate quarry in North Wales offering a contained, current-free dive within an industrial setting. The site features submerged quarry walls and artificial reef structures, with depths ranging from 6 to 19 metres. Visibility typically varies between 5 and 10 metres. Due to the overhead environment created by the quarry walls and potential swim-throughs, buoyancy control is essential. The water remains cold throughout the year, making a dry suit, hood, and gloves recommended. The site is suitable for beginners and supports night diving. On-site facilities include changing rooms, air fills, equipment rental, parking, and toilets, providing a convenient location for training and gear checks.

Llanddwyn Island is a tidal island featuring rocky inlets and secluded coves. This shore-entry site is suited for intermediate snorkellers who can navigate moderate currents and surf. Water temperatures range from 9C to 16C, reflecting the cold conditions typical of the region. Divers and snorkellers should be aware of potential hazards including rip currents, strong currents, and low visibility. The site provides access to parking, toilets, showers, and a cafe. A typical visit lasts approximately 60 minutes. As a tidal location, the topography is best explored during high tide when the rocky inlets are fully submerged.

Porth Ysgaden is a sheltered horseshoe-shaped bay on the Llŷn Peninsula, Pembrokeshire, featuring rocky walls and shallow gullies. This shore-entry site is suitable for beginners, with depths ranging from 5 to 9 metres and an average depth of 5 metres. Divers can expect mild currents and visibility between 3 and 10 metres. The site is accessible via a slipway and offers parking facilities. Night diving is possible, with typical dives lasting around 50 minutes. Water temperatures fluctuate between 9C and 16C throughout the year. Divers and snorkellers should remain aware of boat traffic and potential entanglement hazards in the area.

Blue Lake in Pembrokeshire is a shore-entry quarry dive offering a controlled environment for recreational diving. The site features an artificial reef structure placed on the quarry floor, providing a focal point for exploration. Divers can expect depths ranging from 6 to 12 metres with visibility typically around 5 metres. The water remains cold throughout the year, necessitating appropriate thermal protection such as a drysuit or thick wetsuit. As the site contains overhead environments, divers should maintain awareness of their surroundings and stay within their certification limits. There is no current at this location, making it a practical site for those developing their skills.

Sun Beach in Pembrokeshire is a shore-entry reef dive suitable for beginner divers. The reef topography extends between 10 and 20 metres, with an average depth of 10 metres. Divers can expect mild currents and visibility ranging from 10 to 30 metres. Water temperatures fluctuate between 8C and 18C throughout the year, necessitating a drysuit or a 7mm wetsuit for comfort. As on-site amenities are unconfirmed, visitors should plan to bring their own water and changing arrangements. Remain alert for boat traffic in the vicinity at all times.