The Tunnel in Alghero, Italy, is a versatile dive site featuring a combination of cave, cavern, reef, and wall topography. Accessible by boat, the site offers an average depth of 12 metres with a maximum depth of 18 metres. Divers can explore the varied underwater structures, which are noted for their distinct sunlight effects. Conditions are generally mild, making this an accessible location for beginners. Due to the presence of boat traffic in the area, divers should remain vigilant during ascents and descents. The site is suitable for various experience levels, allowing for different routes through the tunnel and surrounding reef formations.

Grotta di Nereo, located behind the Capocaccia promontory near Alghero, is a complex cave and wall system extending 400 metres. Divers can access the site at depths of 15, 18, and 30 metres, with an average depth of 15 metres and a maximum of 35 metres. The site features large cavernous environments suitable for intermediate divers. Access is strictly by boat, located 200 metres from the shore. Conditions include mild currents and visibility ranging from 10 to 35 metres. Water temperatures fluctuate between 14C and 21C throughout the year. Species recorded around this area include wrasses, Mediterranean morays, common octopus, and various nudibranchs.

Grotta di Nettuno is a complex site near Alghero featuring a combination of cave passages, vertical walls, and drop-offs. Divers typically explore depths between 20 and 30 metres, with visibility ranging from 10 to 30 metres. The site requires advanced open water and cave diving certifications due to the overhead environment within the cave system. Access is exclusively by boat, located 5000 metres from the shore. While currents are generally mild, they can strengthen, and divers must remain vigilant for boat traffic when surfacing. The water temperature fluctuates between 14 and 22C, though the interior of the cave remains a consistent 18 to 20C.

Madonnina in Alghero, Italy, offers a diverse underwater experience featuring a wall that leads into a large cavern. The site is suitable for beginners, with depths ranging from 12 to 19 metres and an average depth of 12 metres. Access is exclusively by boat, and divers should be prepared for moderate currents, particularly when returning to the vessel. The topography includes both reef and overhead environments within the cavern. Species recorded around this area include wrasses, common octopus, Mediterranean moray, great barracuda, various nudibranchs, squat lobsters, and flatworms. Divers should exercise caution due to the overhead environment present within the cavern structure.

Capo Caccia near Alghero features a dramatic wall and drop-off system that extends into complex underwater caves. The site ranges from 16 to 35 metres in depth, requiring advanced certification and specific cavern training for overhead sections. Access is exclusively by boat due to surf conditions. Visibility varies between 10 and 30 metres, with mild currents. Water temperatures fluctuate from 14C to 21C, making a 7mm wetsuit or drysuit advisable outside of the summer months. Divers should maintain strict buoyancy control and remain aware of boat traffic near the surface. Night diving is available at this location.

The Gorgonias is a wall and reef site located off Alghero, Italy, suited for advanced divers. The dive typically requires a negative entry in the blue due to strong currents. Divers descend to a maximum depth of 40 metres to explore the reef before ascending along the wall. Visibility ranges from 10 to 25 metres, and water temperatures fluctuate between 14C and 21C throughout the year. Given the strong currents and depth profile, this site is recommended for experienced divers with appropriate certifications. Boat access is required for all dives, which generally last around 45 minutes.

Cala Inferno is a marine site located beneath the white cliffs of Capo Caccia near Alghero. The topography features a dramatic underwater landscape composed of massive submerged boulders, walls, and caves. Access to this site is strictly by boat. Conditions vary, with moderate currents and potential surf, making it suitable for intermediate snorkelers. Water temperatures fluctuate throughout the year, ranging from 14C in the winter months to 26C in August. The site offers a distinct environment for those exploring the coastal features of the region.

The Colonnade is a versatile dive site near Alghero, Italy, featuring a combination of wall, reef, and cavern topography. Divers navigate through a series of windows, swim-throughs, and arches that create distinct light effects. The site is accessible only by boat, located 1000 metres from the shore. With depths ranging from 5 to 18 metres and an average of 12 metres, it is suitable for beginners. Visibility typically spans 15 to 30 metres. A thermocline is present at approximately 12 metres, where temperatures drop to 15°C. Divers should be aware of sharp coral present at the site. Night diving is available, and typical dive times are around 50 minutes.