Pulau Tidung, one of the island in Pulau Seribu is located very far away, I travel there with kerapung and it takes 2 hours.The sea is so so so blue! It's best in Snorkelling because there are still so many fish and coral, they are all beautifull. A trip to that place isn't expensive at all since you'll be staying at local's homestay with local tour guide that was so friendly!