Well, first of all, the moon revolves around Earth in 27.3 days,
not 30.
Right now, there are four tides ... high, low, high, low ... in roughly
24 hours and 50 minutes. The very rough average is 6 hours and
12 minutes from one extreme tide to the next extreme.
If the moon's period of revolution became only half as long as it
is now, then there would be four tides in roughly 25 hours and
38 minutes ... the very rough average would be 6 hours and
24 minutes between the extremes.
Also ... if the moon's orbital period were only half of what it is
now, that would mean that the moon would have to be much
closer to Earth than it is now. So high tides would be higher,
and low tides would be lower
.
