We spent 3 nights at Captain Nemo's and were very comfortable, despite the rainy weather.
We received an upgrade to a newly renovated room with an outside view window, which was a big plus. It was clean and cozy, with all amenities and even a little more: comfy bed, AC, WiFi, safe, very big fridge, TV with plenty of channels and a DVD player (with hundreds of DVDs available to chose from). Nice bathroom with plenty of hot water. The room was cleaned daily, including changes of towels. Beach towels were also available for free.
The owners are a very welcoming French-Thai couple who love to chat, yet never in an intrusive way. They explained us everything very clearly when we arrived, which was very useful. There is no real reception or a common area in the guesthouse, but the owners were always around during their working hours (from like 8am-6pm) and can give very good advice. They can also arrange tickets for boat and snorkelling trips at discounted prices.
A deposit is charged upon arrival, but you will get it back without any problems as long as you don't destroy anything and none of the guesthouse property of your room is missing.
Philippe, the owner, is currently working on the renovation of all rooms - but don't worry, you won't even notice the renovation works. When making your reservation ask if one of the renovated rooms is available.
The location is as good as it can be, for a guesthouse at this price with all the above mentioned amenities and services, in Koh Tao. You are about 200m uphill from the pier, and another 200m or so meters to the left from the pier there's a beautiful beach for swimming.
Nemo's does not offer bteakfast or any other meals, but restaurants are plentiful, and you can store heaps of food in your fridge if you want to.
There are also other services such as ATMs, post office, a health clinic etc nearby.
Captain Nemo's is a very recommendable guesthouse in Koh Tao for travellers that are on a budget.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.