The islands of Ko Rok Nok, meaning outer, and Ko Rok Nai, meaning inner, are much more than just a convenient overnight stop midway on the passage between Langkawi and Phuket. As they lie in a northeast, Rok Nai, to southwest, Rok Nok, direction they certainly provide safe anchorage in either season and good snorkelling and diving are available throughout the year.
The gap between the two islands is only around 250 metres and there is a half mile long channel with a sandy bottom between 8 and 12 metres which is suitable for anchoring. There are mooring buoys in the channel but the condition of the ground tackle can never be guaranteed so use them with caution or if you have dive gear make a thorough inspection and even take your own line down to the block if you have one.
The best coral is to be found on the east side of Ko Rok Nok and the south and east side of Ko Rok Nai where it is sheltered from the stronger winds and waves of the southwest season. This is where the best snorkelling and the majority of the dive sites can be found. There are also drift dives at the northeast and southwest tips of the group and an interesting dive amongst the boulders in the bay on the west side of Ko Rok Nai.
There is a ranger station on the beach on Ko Rok Nai with simple, but clean, showers and toilets and tents are available for rent for the more adventurous. There is a part time basic restaurant which is more of a shop on occasion, sometimes they have fried rice and on other days all you can buy is soft drinks. There are do it yourself cooking fires but you need to bring your own cooking pots etc. These can be used for a BBQ but please do not light fires on the beach as this is not allowed.
Fourteen miles to the west southwest of the Ko Rok group is the small outcrop of Hin Daeng, meaning red rock. Here three small pinnacles break the surface by less than two metres but drop away quickly beneath the water to a depth of over sixty metres. The fish are abundant and come in many varieties and sizes up to manta rays and even whale sharks.
Around four hundred metres to the southwest is the totally submerged Hin Daeng, or purple rock, named after the coloured anemone that cover the 250 metre long rock. There is normally a mooring buoy marking its position in the northeast season but if not present then the rock runs east to west with pinnacles between 8 and 16 metres and is fairly easy to find with the depth sounder.