When a wave comes in, water is shot up through the hole in a powerful and beautiful geyser like explosion. When the water goes back out, it creates a powerful suction affect. This is what can be very dangerous, as numerous people have carelessly danced around the opening of the hole, only to be sucked out to sea in the blink of an eye.
What NOT to do! Search for the Nakalele Blow Hole on Youtube and you will find plenty of chilling videos of the power of the ocean. The ocean is beautiful and fun, but it also should be feared and respected. Do not do what these foolish tourists are doing. This is exactly what others have done before getting sucked out to sea, never to be seen again.