Righto inter-nerds, what is the go with Perth having only one tide a day for half the month and two tides a day for the other half of the month? Can anyone point me at an inter-nut location explaining it? Google has let me down and I'm trying to settle an argument with a bananabender from work who doesn't believe me. Or type it out here longhand with the credibility to convince a cynical, bitter bastard who thinks the only time he's wrong is when he thinks he's wrong.

Cheers