There are also other factors involved as well like dehydration and fatigue. Once I went to Tioman, have to overnight at Mersing due to tide. For some reason, I cant sleep at all even though I am tired. Next day, have to wait till 9am for the ferry, by the time I reach Tioman, it was almost lunch time. The 1st dive was only about 17 meters and I was out of air by 35mins. I was a shitty day for me. Sunday was back to normal though.