Irregularities in tide levels on coastlines is the result of the alignment of the sun and moon. Exceptionally high tides occur when the sun and moon are aligned during a full moon. This causes the highest of tides on earth. When the sun and moon are at 90 degrees to each other, their gravitational forces are perpendicular. This results in exceptionally low tides, called neap tide.
Another interesting phenomena involving tidal forces and water is the bore tide.
Bore tide occurs when the energy from incoming tides flows up geographically
narrow areas. This includes rivers, and exceptionally narrow inlets
(commonly formed by glaciation events). One example is cook inlet. The alignment of
the sun and moon after a low tide makes for a very powerful incoming tide.
The relatively narrow Turn-again arm and the powerful surge coming in from
the gulf of Alaska creates a large wave of water when the tide comes in.
Photos: Kayaks photo is mine, Diagram is from Wikipedia
