Yes, travel insurance is worth carrying for a beach trip to Nha Trang, and the reasons are mostly about activity and weather rather than any unusual danger in the city itself. Nha Trang is one of Vietnam's best-known coastal resort towns, built around a long stretch of beach and a bay dotted with islands, and diving and water sports are the main activity risk most standard policies need to actually cover.
Diving and snorkeling around Nha Trang bay are genuine draws, popular enough that dive schools and day-boat operators run trips out to the bay's reefs and islands regularly, and this is exactly the kind of activity a baseline travel policy sometimes underinsures. Confirm your policy names scuba diving specifically, including any depth cap, before booking an excursion, since some policies exclude diving beyond recreational limits or without certification.
Nha Trang has local hospitals capable of routine and moderately serious care, but anything requiring specialist treatment is typically referred onward to Ho Chi Minh City, the country's larger medical hub several hours south by road or a short flight. Confirm your policy covers transfer between Vietnamese facilities rather than assuming local care is sufficient for anything complex. Sun exposure and heat-related illness are common minor claims for beach visitors here, and standard medical cover handles these routinely, though it is worth confirming your policy covers boat-based day trips out to the bay's islands alongside diving specifically.
The wet season along Vietnam's south-central coast runs roughly October through December, bringing heavy rain and occasional flooding that can disrupt beach plans and inland travel alike; trip-delay cover is worth checking for a visit in this window. Keep any clinic paperwork, dive-operator incident reports, and receipts for treatment, and check whether your policy requires notice before non-emergency transfer to Ho Chi Minh City is arranged.