Ordered from nearest — out to see the real thing
Sorted from closest to furthest, with an honest note on which is half a day, which is a full day, whether to take a longtail or speedboat, and roughly what tours cost.
If you only make one trip out to sea, make it this one. Leaving Ao Nang, you stop at four spots in a single outing — Phra Nang (a white-sand beach below the cliffs with a shrine in its cave), Chicken Island (named for a rock shaped like a chicken's head), and Tup and Poda islands, both with white sand and clear water good for snorkelling.
The highlight is the sandbar (talay waek) — at low tide a strip of sand surfaces to link Chicken, Tup and Mor islands so you can walk across, depending on the day's tide. To be honest, this trip draws crowds and several of the islands are shallow, so it suits families and first-timers; take a morning departure for fewer people and gentler sun.
For the prettiest sea picture in Krabi, many people point to the Hong Islands — a group of limestone islands within Than Bok Khorani National Park. The highlight is the lagoon at the centre, where the cliffs close into a ring so the water inside turns still and emerald; you can kayak or take a boat inside at high tide.
The other thing not to miss is the 360-degree viewpoint, a short climb up a rise that opens onto the lagoon and all the surrounding islands — a fine view. Around the islands there are white-sand beaches and snorkelling spots too. Honestly, the Hong Islands are a little further than the Four Islands and usually a full-day trip, but worth it for prettier water and fewer people than the Four-Island run.
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Phi Phi is the most famous name in these waters, and it's closer from Krabi than from Phuket. The headline stop is Maya Bay, the beach made famous by the film The Beach, walled in by tall limestone cliffs. Around the islands lie snorkelling spots over coral and fish, Loh Samah Bay, Viking Cave, and the Phi Phi Don viewpoint.
Honestly, Phi Phi gets very busy in the middle of the day, and Maya Bay in particular opens in timed slots with caps on visitor numbers (check the current status before you go, as the bay was closed for recovery in the past). The trick is to pick a tour that leaves early and arrives before the big boats from Phuket. We have a separate page on visiting Phi Phi from Krabi — read it before you decide.
Ko Lanta differs from the others on this list because it's a large island with roads and places to stay, not a small islet you visit only by day. The mood is more relaxed, the beaches long and quiet, and it suits anyone who wants to escape the bustle of Ao Nang or Phi Phi. The south of the island holds Mu Ko Lanta National Park and a lighthouse with a walkable viewpoint.
From Lanta you can run further tours to nearby islands such as Ko Rok and Ko Haa, where the water is very clear in the dry season. Honestly, doing Lanta as a day return from Ao Nang is tiring and not great value, since it means a car and a ferry; Lanta is better for anyone who can stay a night or two. Read our day trips from Krabi to plan Lanta in.
Bamboo Island is a small island north of the Phi Phi group. Its appeal is the fine white sand and shallow, clear water you can easily wade into — good for sunbathing and snorkelling right off the beach. It photographs beautifully, the white sand set against turquoise water.
Most of the time Bamboo Island is included in a full-day Phi Phi tour as the last stop before heading back; few tours run to Bamboo on its own from Krabi. Be honest with yourself: there's almost no shade on the island and few facilities, so bring a hat, sunscreen and your own water. It sits within the same national park as Phi Phi, so there's a fee to pay here too.