| Tide tables provide predicted times and heights of the high and
low waters associated with the vertical movement of the tide. These tables are
necessary for obtaining the depth of water under the keel or over a shoal, for
anchoring and for establishing appropriate times for beaching a boat.
Current tables provide predicted times for slack water and the times and
velocities of maximum current, all of which are associated with the horizontal
movement of the tide. This information is necessary for efficient navigation,
especially when under sail. It is required when navigating narrow passes or
channels that have strong currents and for safety considerations when the wind
is against the current. Where strong currents are present with a strong wind
opposing the flow, extremely large, steep waves may be generated that can be
particularly dangerous to small craft.