Southwest Pinnacle

Image credit: Wikimedia Commons

Overview

Located approximately 13 kilometers (8 miles) southwest of Koh Tao, Southwest Pinnacle is one of the island’s premier offshore dive sites. Unlike the single massive monolith of Chumphon Pinnacle, Southwest consists of a series of staggered, submerged granite rock formations. The central, largest pinnacle rises to within 5 meters (15 feet) of the surface, while the surrounding smaller pinnacles step down gradually to a sandy seabed at approximately 30 meters (100 feet).

Because the entire structure is fully submerged in the open Gulf of Thailand, Southwest Pinnacle is exposed to shifting ocean currents and variable surface conditions. Due to the depth of the outer rocks and the potential for strong water movement, the site is generally recommended for divers holding an advanced certification. It is not an appropriate location for the confined water or initial open water dives of an open water course. However, for experienced divers looking for the best places to learn how to navigate complex, multi-pinnacle environments while managing deeper profiles, this site is highly regarded by local instructors.

The Dive Experience

Accessing Southwest Pinnacle requires a boat transit of roughly 40 to 50 minutes from the main piers on Koh Tao. The dive typically commences with a descent down a mooring line attached to the main central pinnacle. From there, the dive profile usually involves a slow, spiraling circumnavigation of the various rock formations, starting at the deeper outer pinnacles and gradually working upwards to the shallower central structure to complete the safety stop.

Because it is an offshore site, visibility can be variable, generally ranging from 10 to 20 meters, depending heavily on tidal movements and seasonal plankton blooms. Water temperatures are very warm, consistently averaging between 27°C and 30°C (81°F to 86°F). Divers should consult a travel and packing guide; a dive computer is essential for tracking nitrogen absorption during the multi-level profile, and carrying a surface marker buoy (SMB) is highly recommended due to the potential for choppy surface conditions and boat traffic upon ascent.

What You’ll See

The visual signature of Southwest Pinnacle is its extraordinary covering of sea anemones. The upper sections of the granite rocks are almost entirely carpeted in magnificent sea anemones (Heteractis magnifica) in vibrant shades of pink, green, and blue. These anemone fields host thousands of pink anemonefish, creating a highly colorful and dynamic environment in the shallower portions of the dive.

Beyond the anemones, the site supports massive aggregations of schooling fish. Divers frequently encounter vast, swirling schools of yellowtail barracuda, fusiliers, and snappers circling the rock formations. Large Malabar groupers are commonly found lurking in the deep shadows and crevices at the base of the pinnacles.

Southwest Pinnacle also shares a reputation with Chumphon Pinnacle and Sail Rock as a primary location for encountering whale sharks (Rhincodon typus). During the peak season (typically March through May), these massive animals are occasionally spotted cruising through the channels between the pinnacles, filtering plankton from the nutrient-rich water.

Planning Your Dive

Southwest Pinnacle is a staple on the schedules of most dive centers operating on Koh Tao. Trips are typically organized as two-tank morning dives, often paired with a shallower local site on the return journey to the island. As with all sites in the region, divers must adhere to local environmental protocols, maintaining strict buoyancy control to avoid damaging the dense anemone fields that cover the rock surfaces.