Great — for an “ultimate” beach vacation in Sri Lanka you’ll want to match the coast to the season and your vibe (surfing, snorkeling, luxury, or quiet). Below I’ve grouped the best places to stay by coast, with what each area is best for, when to go, lodging styles to look for, and practical tips.

Best coasts and towns (what to expect)

• South & southwest coast — Mirissa, Weligama, Unawatuna, Hikkaduwa, Galle

  • Best for: swimming, snorkeling, whale/dolphin watching (Mirissa), easy surf for beginners (Weligama), nightlife and restaurants (Unawatuna/Hikkaduwa), Galle Fort culture.
  • Vibe: palm-fringed bays, beach bars, boutique guesthouses to high-end resorts. (srilankaholidaystours.com)

• East coast — Arugam Bay, Trincomalee (Nilaveli, Uppuveli), Pasikudah/Kalkudah

  • Best for: world‑class point breaks and surf culture (Arugam Bay), calm shallow bays and snorkeling (Pasikudah), diving and quieter beaches (Trincomalee).
  • Vibe: surf camps and laid‑back beach bungalows in Arugam Bay; more tranquil, shallow-water resorts in Pasikudah. (feelfreetravel.com)

• West coast / near the airport — Negombo, Bentota

  • Best for: convenient arrival/departure stays (Negombo), river safaris and water sports (Bentota), family‑friendly resorts.
  • Vibe: more developed, good for the first/last night. (thetimes.co.uk)

• North & Northeast — Jaffna, Nilaveli (Trincomalee)

  • Best for: quieter, less-touristed beaches, cultural exploration combined with beaches. Best travel window differs from south. (visitsrilanka.ai)

When to go (season advice — important)

• South & west coasts: best December–April (calm seas, best snorkeling/whale season). Peak weather Jan–Feb. (srilankaholidaystours.com)
• East coast: best May–September (dry season there, prime surf at Arugam Bay and calm waters at Pasikudah). (nichevoyager.com)
• Shoulder months (April and September–October) can offer fewer crowds and lower prices but bring mixed weather — good value if you’re flexible. (srilankaholidaystours.com)

Where to stay by travel style

• Luxury / honeymoon: pick boutique resorts or small luxury properties on Mirissa, Galle/Koggala, or Pasikudah that offer beach villas, private pools, spa services, and private dinners.
• Mid‑range / boutique: boutique guesthouses, converted colonial villas (Galle Fort area), beach bungalows in Weligama or Unawatuna — stylish, local character, good service.
• Budget / backpacker: surf hostels, guesthouses, and surf camps in Weligama, Arugam Bay, Hikkaduwa — social and wallet-friendly.
• Surf trip: Arugam Bay (May–Sept) or Weligama/Hikkaduwa (Nov–Apr) — look for surf camps that include boards, lessons, and transfers. (feelfreetravel.com)

Practical travel tips

• Book the right coast for the month you plan to visit — Sri Lanka’s two monsoon patterns mean different coasts are best at different times. (Repeat: south/west Dec–Apr; east May–Sep.) (srilankaholidaystours.com)
• Getting around: internal flights (Colombo ↔ Trincomalee) save time; trains on the south line (Colombo → Galle → Matara → Mirissa) are scenic but can be slow; tuk‑tuks are handy for short trips. (cntravellerme.com)
• Health & safety: swim only where the beach is flagged safe; ask locally about currents. Use reef‑safe sunscreen for marine protection.
• Visas and entry: Sri Lanka has been running tourist visa initiatives; check the current visa policy before booking (policies have changed in recent years). (cntraveler.com)
• Wildlife & activities: Mirissa is best for whale watching in the south‑west season; snorkel/ dive spots are excellent off Hikkaduwa, Nilaveli, and Pasikudah. (srilankaholidaystours.com)

Quick sample itineraries

• 10 days — South coastal highlights: Colombo → Galle (2 nights, Galle Fort) → Mirissa (3 nights: beaches + whale watching) → Weligama/Unawatuna (3 nights: surf/snorkel) → back to Colombo.
• 10 days — Surf & chill (east season): Colombo → Arugam Bay (5–6 nights surf + relax) → Trincomalee or Pasikudah (3 nights snorkeling/calm water) → Colombo.

If you want, I can:

• Suggest specific hotels and guesthouses across budgets for the exact dates you’re considering (I’ll check availability and current reviews), or
• Build a day‑by‑day beach itinerary (including transfers and activities) for the exact length of trip you want.

Which coast or travel style appeals most to you?