Yes, because of gravity. Most all oceans and seas touch each other somewhere

I respect the answers of the experts, they are correct when all these factors are judged. Tides always move in & out and G will always be there. But when measuring something that cunsumes 2/3rds of our planet whats a few inch variation Just My Opinion Thanks

here is a tendency to think of sea level as a uniform surface around the world that is used as a datum from which land elevations and ocean depths are measured. Actually sea level is not the same everywhere and it also moves up and down with time. Ocean levels in the Pacific are slightly higher than in the Atlantic and ocean levels near the equator are higher than those at the poles. The factors that spatially influence ocean levels include oceanographic conditions (currents), meteorological conditions (atmospheric pressure, wind), terrestrial conditions (river discharge), and geophysical conditions (geoid anomalies). The factors that influence temporal sea level fluctuations range from high frequency (daily, seasonal) astronomical tides to low frequency changes in global climate. Major climatic (atmospheric temperature) fluctuations over periods of thousands of years cause global sea level to fall and then rise as continental ice sheets form and subsequently melt.

The accurate term for a tide gauge record is relative sea level change because it includes the combined movement of both water and land. Even if sea level was constant there could be changes in relative sea level. For example, a rising land surface would produce a relative fall in sea level, whereas a sinking land surface would produce a relative rise in sea level.

Note:Thats what I practically did when surveying hills during my Civil Engineering course.

No they are not, as the the moon orbits the Earth its gravity pull causes a buldge in the level of the water. The sun is also affecting the buldge.

Tides and Water Levels

Gravity, Inertia, and the Two Bulges



Two tidal bulges are created on opposite sides of the Earth due to the moon's gravitational force and inertias counterbalance. Click the image for a larger view.


Gravity is a major force responsible for creating tides. Inertia, acts to counterbalance gravity. It is the tendency of moving objects to continue moving in a straight line. Together, gravity and inertia are responsible for the creation of two major tidal bulges on the Earth (Ross, D.A., 1995).

The gravitational attraction between the Earth and the moon is strongest on the side of the Earth that happens to be facing the moon, simply because it is closer. This attraction causes the water on this “near side” of Earth to be pulled toward the moon. As gravitational force acts to draw the water closer to the moon, inertia attempts to keep the water in place. But the gravitational force exceeds it and the water is pulled toward the moon, causing a “bulge” of water on the near side toward the moon (Ross, D.A., 1995).

On the opposite side of the Earth, or the “far side,” the gravitational attraction of the moon is less because it is farther away. Here, inertia exceeds the gravitational force, and the water tries to keep going in a straight line, moving away from the Earth, also forming a bulge (Ross, D.A., 1995).

In this way the combination of gravity and inertia create two bulges of water. One forms where the Earth and moon are closest, and the other forms where they are furthest apart. Over the rest of the globe gravity and inertia are in relative balance. Because water is fluid, the two bulges stay aligned with the moon as the Earth rotates (Ross, D.A., 1995).

The sun also plays a major role, affecting the size and position of the two tidal bulges. The interaction of the forces generated by the moon and the sun can be quite complex. As this is an introduction to the subject of tides and water levels we will focus most of our attention on the effects of the stronger celestial influence, the moon.