On big days it is always good to have an exit strategy. In Costa Rica I have stayed out for hours on big swells, and if you are ignorant of tide, you can get dry docked on boulders that you were surfing over an hour or so ago, and the long climb back to shore over exposed slippery rocks can be a biotch. That's what happens sometimes when you're greedy and stay out too long.
Outside of rising and lowering water level, inlets and openings to bays have are very influencial to nearby breaks, and are highly influenced by the currents created by the moving tides. For example, when the tide is coming in to the inlet, then it creates a fast current, which has significant impact on the swells moving toward the current. In some cases, it can focus the swells and in other circumstances swells will refract away from the current. Large openings to bays can have a larger scale influence.
The interactions of currents and nearshore waves are one of the more complex aspects of wave mechanics, where local experience certainly holds an edge.