True tides—changes in water level caused by the gravitational forces of the sun and moon—do occur in a semi-diurnal (twice daily) pattern on the Great Lakes. Studies indicate that the Great Lakes spring tide, the largest tides caused by the combined forces of the sun and moon, is less than five centimeters in height.

Yes, lakes can indeed have both tides and currents, though they are usually much less pronounced than those in the ocean. True tides, caused by the gravitational pull of the moon and sun, do occur in large bodies of water like the Great Lakes, but they are typically less than 5 centimeters (2 inches) in height. These are often "masked" by much larger water level changes caused by wind and atmospheric pressure. A more common phenomenon in lakes is a seiche (pronounced "saysh"), which is an oscillating wave that sloshes back and forth across the lake, often mistaken for a tide. Currents are very common in lakes and are primarily driven by wind, temperature differences (thermal stratification), and the inflow or outflow of rivers. In the Great Lakes, for example, powerful "rip currents" can form near piers and breakwaters, posing a significant danger to swimmers. Surface currents are often driven by the "Coriolis effect" in very large lakes, creating circular patterns similar to oceanic gyres. While smaller lakes may appear still, they are dynamic systems with constant, albeit subtle, water movements.