Get PADI certified — Open Water courses from ~$250 at dive shops like Sailing Club Divers or Vietnam Active

Swim and snorkel at Hon Mun Island (marine protected area)

Try nem nuong (Nha Trang-style grilled pork rolls)

Island hopping booze cruise — the classic backpacker experience (~$10–15)

Beach day — rent a lounger or just use your towel on the public beach