These activities are related to the knowledge of tides and current required by Coxswains when operating commercial vessels.
Please make sure you watch the tides Video AT THIS LINK before you complete these activities.
Tide table usually give the time of High and Low water during diurnal and semi diurnal periods. Tide tables also identify Spring and Neap time during different phases of the Moon. Therefore there could be 6 or more hours between tides.
Coxswains should be able to calculate, using simple maths calculations of add and subtract, to determine the height of tide at any time during the high and low tide times to ensure there is a safe and sufficient depth of water under the vessel's keel.