Beaches on two coasts, two different seasons
Sri Lanka’s geography creates a useful situation for beach planning: the southwest coast (Mirissa, Unawatuna, Hikkaduwa) is best November to April, while the east coast (Trincomalee, Arugam Bay) is best May to October. This means there is almost always a beach destination in good weather somewhere on the island.
Southwest Coast: the classic choice
Mirissa is the most popular — a beautiful crescent bay with good surf, whale watching (blue and sperm whales from December to April, the best whale watching I have done anywhere), and excellent seafood restaurants on the beach. Unawatuna has a sheltered bay that is better for swimming than Mirissa. Tangalle is more remote and quieter. Hiriketiya is a small horseshoe cove that has become the surf crowd’s favorite.
East Coast: the less-visited alternative
Arugam Bay on the east coast is a world-famous surf break (best July-September) with a relaxed backpacker scene. Trincomalee has a spectacular natural harbor and some of the most pristine beaches in Sri Lanka — Uppuveli and Nilaveli are largely undeveloped despite being beautiful. The east coast sees far fewer tourists than the south and southwest.
Galle: beaches plus history
Galle Fort itself has no beach, but it is the best base for the southwest coast — a 45-minute drive from Mirissa, excellent restaurants and boutique hotels within the Dutch colonial walls, and a genuinely interesting town to explore. Stay inside the fort and day-trip to beaches.