The Tun Sakaran Marine Park is perhaps one of the most underrated diving destinations in Sabah. It doesn't get as much attention as Sipadan, but it is equally stunning underwater. The marine park consists of eight islands and while you are there, you should definitely go hiking in Boheydulang. The 600-metre trail takes about 40 minutes. It is a bit of a challenge when it gets steep, but trust me the view from the top is absolutely worth a million dollars.