Koh Samui serves as a convenient base for diving in the Gulf of Thailand. The surrounding waters — including Ang Thong Marine Park and the small islands off the southern coast — offer sites suitable for beginners and certified divers alike.

Key Dive Sites Near Samui

Mu Ko Ang Thong National Marine Park

An archipelago of 42 islands about 30 km northwest of Samui. Crystal-clear water, healthy coral gardens, and diverse marine life make it one of the region's top spots for snorkeling and recreational diving. Depths range from 5 to 20 meters; visibility can reach 15–20 m in season.

Koh Tan & Koh Madsum

Small islands off Samui's southern tip. Shallow coral reefs make them ideal for beginners and snorkelers. Most Samui dive centers run regular day trips here.

Sail Rock (Hin Bai)

A submerged pinnacle between Samui and Koh Phangan, famous for whale shark encounters (especially April–October). Reachable on day-trip liveaboard excursions from Samui.

Best Season

March through October offers the best visibility. During the northeast monsoon (November–January), the western side of the gulf tends to be calmer; Samui's east coast can see rougher conditions.

Dive Certifications & Courses

Local dive centers offer beginner courses (PADI/SSI Open Water) as well as specialty programs for certified divers: night dives, underwater photography, and reef ecology. A two-tank day trip typically costs 2,500–4,000 THB; Open Water courses run 12,000–16,000 THB.