Great — here are the best beach areas in Sri Lanka where you can stay at a beachfront resort and have easy, reliable access to scuba diving and snorkeling, with notes on what to expect and a few example dive operators/resort pointers.

Summary (quick)

• East coast (Nilaveli / Uppuveli / Trincomalee / Pigeon Island) — excellent snorkeling (Pigeon Island), calm waters in the east coast season, several PADI 5‑Star centres operating from beach resorts. (Divinguru.com)
• South / southwest (Hikkaduwa, Unawatuna, Mirissa, Galle) — many reef sites and wreck dives, strong resort + dive‑centre scene, best November–April for calm seas. (internationaldivingschool.com)
• Passikudah (east coast bay) — shallow calm bay good for snorkeling; dive/snorkel trips are available from local operators and several beachfront resorts. (thetimes.co.uk)

Recommended areas and what you’ll find

1. Nilaveli / Uppuveli / Trincomalee (northeast)

• Why go: Direct boat access to Pigeon Island National Park (fantastic reef snorkeling — turtles, reef sharks, colorful fish) and beginner‑friendly dive sites. Several PADI 5‑Star dive centres operate from beach resorts here. (Divinguru.com)
• Typical resort setup: beachfront hotels/resorts that either host an on‑site dive centre or work with nearby PADI centres (daily boat trips to Pigeon Island). Example operator: Divinguru Nilaveli. (Divinguru.com)

2. Hikkaduwa (southwest)

• Why go: Long established dive/snorkel destination: shallow coral gardens, shipwrecks and abundant marine life; many PADI centres and walk‑on snorkeling right off the beach. Best season Nov–Apr. (internationaldivingschool.com)
• Typical resort setup: a wide range from budget guesthouses to mid‑range and luxury beachfront hotels; dive centres run daily boat dives and shore snorkel trips. Example operators: International Diving School, Deep Blue/Hikkaduwa dive centres. (internationaldivingschool.com)

3. Unawatuna / Galle (south coast)

• Why go: Good wreck dives and reef/snorkel sites close to Galle; Unawatuna has established PADI dive centres and easy access from many beachfront resorts. (unawatunadiving.com)
• Typical resort setup: many resorts in Unawatuna/Galle partner with PADI dive centres for courses, fun dives and snorkeling trips.

4. Mirissa / Weligama (south)

• Why go: Good snorkeling (turtles), dive operators offering PADI courses and boat dives; Mirissa is also a major whale‑watching base (separate trips). Dedicated dive centres run turtle snorkeling and beginner dives. (mirissadivingandsnorkelingcenter.com)

5. Passikudah / Kalkudah (east coast bay)

• Why go: Very shallow, calm bay — excellent for easy snorkeling straight from the beach; some resorts provide snorkel gear and organise boat trips to nearby reefs. Best visited in the east coast season. (thetimes.co.uk)

Practical notes

• Seasons: south/west (Hikkaduwa, Unawatuna, Mirissa, Galle) are generally best November–April; east/northeast (Nilaveli, Trincomalee, Passikudah) are best May–October. Plan by season for calm water and best visibility. (thetimes.co.uk)
• Certification & beginners: most dive centres run Discover Scuba (intro) and full PADI Open Water courses; snorkeling trips are available for non‑swimmers with guides. (unawatunadiving.com)
• Conservation & safety: many leading centres in Sri Lanka hold PADI awards and Project AWARE commitments — look for PADI‑affiliated and Green‑star operators if reef health and safety are important. (travel.PADI.com)

If you’d like, I can:

• Give a short list of specific beachfront resorts (by budget level) in any one of these areas that are known to host or directly partner with dive centres; or
• Find available resorts that have on‑site dive centres or guaranteed daily snorkeling trips for your travel dates — tell me which area(s), travel dates, and budget and I’ll look them up.