Short answer
Plan two nights for the essentials (one bay day, one island day), three for a relaxed pace and four or more if you want a night on the water, the Viet Hai trek or climbing.
01One day (one night)
Afternoon arrival
Check in, walk the harbour and climb to Cannon Fort for the late light over the bay.
Evening
Seafood along the waterfront or at the night market. Book tomorrow's boat at your hotel or a tour desk.
Full day on Lan Ha Bay
A boat trip with kayaking, a lunch stop and a swim at a sheltered cove. Most return by mid-afternoon, just in time for the bus back to Hanoi.
02Two days
Day 1
Arrive, settle in, then walk over the headland to the Cat Co coves for a swim and sunset.
Day 2
Lan Ha Bay by boat: Cai Beo, kayaking through lagoons and a beach stop.
Day 3 morning
Scooter or driver to Ngu Lam Peak for the view, then Hospital Cave on the way back. Afternoon bus to Hanoi.
03Three days
Day 1
Arrival, Cannon Fort at sunset, dinner in town.
Day 2
Full day in Lan Ha Bay, ideally on a small boat with more kayaking time.
Day 3
National park morning, Hospital Cave and Trung Trang Cave, then the quiet west coast and Xuan Dam by scooter. Evening squid fishing trip in summer.
Day 4 morning
A slow breakfast and a swim before the bus.
04Four days or more
A night on the water
Swap a hotel night for an overnight boat in Lan Ha Bay, with sunset kayaking and a quiet anchorage.
The long walk
Trek through the national park to Viet Hai village and return by boat across the bay.
Rock day
A guided climbing session at Butterfly Valley or deep water soloing from a boat, depending on tide and season.
Loose ends
The island road loop, Monkey Island, a massage and the beach.
05If it rains
Swap the order: keep bay days for the best forecast and use wet spells for caves, the market and cooking or massages in town. Our rainy day ideas has more. In summer, rain usually comes in bursts, so a boat trip in light rain can still be lovely.
?Questions people ask
Is one night on Cat Ba enough?
It is enough for a single Lan Ha Bay boat trip, but you will spend almost as long travelling as exploring. Two nights is far better value.
Should I do a cruise or stay on the island?
Stay on the island if you want hiking, climbing and town life with day trips on the bay. Choose a one-night cruise if the bay itself is the point and you want a sunset and sunrise on the water. Many people do both.