Portland offers a diverse range of marine environments including wrecks, reefs, and drift sites located off the South Coast of England. Divers can explore depths ranging from 5 to 30 metres, with an average depth of 28 metres. Access to these sites is strictly by boat, as they are situated approximately 100 metres from the shore. Conditions are variable, with visibility fluctuating between 1 and 20 metres and strong currents present. Due to the challenging nature of the currents and potential for entanglement, this site is best suited for intermediate divers. Water temperatures range from 9C to 18C throughout the year, necessitating appropriate thermal protection.

The Gertrude Wreck is a combined wreck and reef site located off the South Coast of England. Resting at depths between 6 and 14 metres, the site is suitable for intermediate divers. Access is by boat, which is required due to its distance of 2450 metres from the shore. Divers can expect mild currents, though these may strengthen, and visibility typically ranges from 5 to 15 metres. Water temperatures fluctuate between 9 and 18C throughout the year. Due to the wreck structure, there is a risk of entanglement, and divers should carry a line cutter. Species recorded around this area include European Common Cuttlefish, Gray Seal, wrasses, and various crustaceans.

Portland Harbour offers a diverse underwater environment featuring a mix of natural reefs, wrecks, and artificial reef structures. Depths range from 2 to 14 metres, with an average of 10 metres, making it suitable for beginners. Divers can access the site via boat or shore. Visibility varies between 2 and 10 metres, and currents are generally mild. The site supports night diving and provides comprehensive facilities including showers, rinse stations, and air fills. Due to significant boat traffic, divers must tow a surface marker buoy at all times and remain vigilant during ascents. Always check harbour authority notices before entering the water.

The James Fennel Wreck is a boat-accessible dive site located 1000 metres off the coast of Swanage and Poole. This wreck and reef site sits at an average depth of 15 metres, with a total depth range between 14 and 18 metres. Divers can expect mild currents and visibility ranging from 5 to 30 metres. The site is suitable for beginners and typically offers a 45-minute dive duration. Facilities available in the area include parking, toilets, showers, changing rooms, air fills, dive shops, boat charters, and guided tours. Water temperatures fluctuate seasonally between 9C and 18C.

The Cragside is a wreck dive site located 50 metres from the shore near Swanage and Poole. This site is suitable for beginners, with an average depth of 7 metres. Access is by boat only. Conditions vary, with visibility ranging from 2 to 10 metres and mild currents. Water temperatures fluctuate between 9C in the winter and 18C during the summer months. Divers should be aware of potential hazards including boat traffic and the risk of entanglement. Facilities available in the area include air fills, showers, toilets, a cafe, guided tours, and boat charter services.

The Sidon is a submarine wreck located 11.2 kilometres off the coast of Swanage and Poole. This artificial reef site sits at depths ranging from 27 to 36 metres, with an average depth of 34 metres. Access is strictly by boat. Divers should be prepared for moderate currents and visibility that varies between 5 and 20 metres. Due to the depth and potential for entanglement, this site is suitable for intermediate divers. Water temperatures fluctuate throughout the year, ranging from 9C in late winter to 18C in September. Boat charters and air fills are available in the region to support dives at this location.

Durdle Door is a geological landmark featuring a natural arch, rocky gullies, and a small cavern on the Man O War side. Divers can explore depths ranging from 5 to 15 metres, with an average depth of 10 metres. The site is accessible from the shore, though it requires a swim of approximately 800 metres. Conditions are variable, with strong currents, surge, and surf present. Due to the overhead environment of the cavern and potential rip currents, this site requires careful planning. Water temperatures remain cold throughout the year, ranging from 9C to 18C, necessitating appropriate thermal protection for all divers.

Man O'War Cove is a crescent-shaped bay located near Durdle Door, defined by a partially submerged offshore reef. This site is suitable for intermediate divers and snorkellers, with depths ranging from 7 to 14 metres and an average depth of 7 metres. Access is via the shore, with the reef situated approximately 100 metres out. Conditions vary, with moderate currents and visibility typically starting at 6 metres. Water temperatures fluctuate between 9C and 18C throughout the year. Facilities available at the site include parking, toilets, and a cafe. Hazards to consider include the potential for rip currents, surf, and strong currents.