The feeder is usually the longshore current that flows parallel to the beach inside the breakers. The neck is the main channel of the rip current where feeder currents converge and flow outwards at a speed of one to three knots through a weak point in the breakers. The head is where the current widens and slackens outside the breaker line. A number of swimmers are lost every summer when caught up in rips and swept out to sea. If trapped in this situation, swim parallel to the shoreline until out of the rip rather than swimming directly into the current, then swim back to shore.
Tides are the slow, periodic vertical rise and fall of the sea surface.
They are usually described as being either diurnal or semi-diurnal. Tidal ranges along the shoreline vary by location. For example, the tides in Canada's Bay of Fundy, an Atlantic Ocean inlet west of Nova Scotia, rise and fall as much as 50 feet, while the tidal range in Lake Superior is measured in inches. The position of these celestial bodies results in significant variations in pulling forces causing above or below normal tidal ranges. The range between a high and a low tide is greatest when the sun, moon and Earth are in alignment.