The reason to eat in Dadonghai is seafood. The streets one block back from the beach — particularly along Yuya Road — are lined with open-fronted seafood restaurants where the catch sits in tanks and basins out front. You point at what you want, agree a price by weight (always confirm the per-jin rate before they cook), and choose how it should be cooked.
The classic order is steamed prawns, garlic-and-glass-noodle scallops, salt-and-pepper mantis shrimp, and a fish steamed Cantonese-style with ginger and spring onion. Hainanese chicken rice — the original of the dish that became Singapore's national plate — turns up on most menus too. Coconut Chicken Hot Pot is another local speciality worth trying. Expect to pay 150-250 yuan a head for a proper seafood feed; the same meal in Beijing or Shanghai would cost three times as much.