I think I will be quite tired after a big day doing mountain bike and trekking.
But I will have time to sleep when I will die 🙂
So, I checked on the webpage of Vietnam Active which is the company I saw for the tour in mountain bike.
They are also doing some PADI diving courses and one of them which is cheap (35 USD) is a Night Beach Dive. I think it can be fun at night to see the fishes and corals with the head lamps. It is something I have never done before so it would be the good opportunity.