Thanks Bones for the information, I know there are more dangerous sea creatures that we should be aware of.. like the fire corals which I was not aware of until Jail666 mentioned to me in Redang..
Once while I was skindiving for crabs in Johor, I came face-to-face with a sea snake, light beige with greenish tinge, with a flat tail. I was looking for crabs around a stone, and as I look up, there it was, inches from my mask. It bolted away, and so did I.
Later did I found out that it was an Olive Sea Snake, one of the most venomous snakes in the sea...I was lucky..