High
and
low
tidesTide results from the gravitational effects of the moon and, to a lesser extent, the sun. As it orbits the earth, the moon pulls most strongly at the water directly below it, raising the water, and it pulls most weakly at the water on the opposite side of the earth, raising that water also. As the earth makes one daily turn beneath the moon, each place on earth goes from closest to farthest and back again, experiencing two high tides with two low tides in between. Since the moon orbits the earth every 28 days, and does so in the same direction that the earth rotates, the actual time for this complete daily cycle is 24 hours plus one- 28th of a day (about 50 minutes) and so the tides come about 50 minutes later each day.
Spring
and
neap
tidesDuring a new moon or a full moon, when the moon aligns with the sun, gravity of the sun adds to the pull of the moon making high tides higher, or spring tides. At the time of a 1st or 3rd quarter moon, when the sun’s pull forms a right angle to that of the moon, gravity of the sun subtracts from the pull of the moon and tides are lower, or neap tides.
and slack current Along with tides come tidal currents that flow as the tide rises and ebb as it falls. Peak current occurs midway between the slack waters of high and low tide and can often be several knots. The height of tide ranges from a few inches in parts of Florida to more than 30 ft in parts of Nova Scotia. It can rise higher, and fall lower, than the mean high and low water soundings shown on charts. State and height of the tide is important when anchoring, tying up to a non-floating dock, entering a shallow channel, and passing under a bridge, for example. State of the tidal current can have a huge effect on boat speed. Data about tides and currents traditionally came from tables published for particular places but today is more easily obtained from chart plotter data. Symptoms of seasickness Seasickness Some people never get seasick. Some always get seasick. Most fall in between. At least half the crew will be seasick on a typical offshore passage. Women get seasick faster.