The water in ocean is typically at a lower elevation than water on land, and some maps show elevation asl (above sea level). It’s the force of gravity that moves water from higher elevation to lower elevation. Water sometimes is retained in depressions such as wetlands, ponds or lakes, and its connectivity with ocean not clear as water may be evaporated before it can move laterally or downward to stream or groundwater. The movement of water across land also has concentrated into lowest areas as it moves, and exerted power to erode as it moves from slopes and headwaters downstream in rills, gullies, channels, streams and rivers. Dave Rosgen at www.wildlandhydrology.com has classified various valley and stream types that describe the differences evident from the channel forming processes as water moves across the landscape. In coastal areas, high tides and landward driven winds and storms can move ocean waters into estuaries and sometimes portions of nearby low gradient coastal streams due to the temporary differences in higher ocean elevation as compared to the lower estuary and other low elevation coastal channels. The sea water is heavier, and is sometimes referred to as the wedge, as the lighter fresh waters are on the surface unless mixing occurs. In a few places, the land is lower than the ocean, so these areas can capture and contain water, preventing flow toward the oceans. Some water that is absorbed on land helps to recharge groundwater, and some of this may eventually return to streams or the ocean, but some is retained in soils, evaporated or transpired, or retained in aquifers, sometimes for extended periods of time.

Land cools down rapidly and the air above the land becomes cooler. Sea water cools down slowly so, the air above the sea is hotter and has a lower air pressure as compared to air pressure above the land. Therefore, cooler air present over land flows towards sea.

The water in ocean is typically at a lower elevation than water on land, and some maps show elevation asl (above sea level). It’s the force of gravity that moves water from higher elevation to lower elevation. Water sometimes is retained in depressions such as wetlands, ponds or lakes, and its connectivity with ocean not clear as water may be evaporated before it can move laterally or downward to stream or groundwater. The movement of water across land also has concentrated into lowest areas as it moves, and exerted power to erode as it moves from slopes and headwaters downstream in rills, gullies, channels, streams and rivers. Dave Rosgen at www.wildlandhydrology.com has classified various valley and stream types that describe the differences evident from the channel forming processes as water moves across the landscape. In coastal areas, high tides and landward driven winds and storms can move ocean waters into estuaries and sometimes portions of nearby low gradient coastal streams due to the temporary differences in higher ocean elevation as compared to the lower estuary and other low elevation coastal channels. The sea water is heavier, and is sometimes referred to as the wedge, as the lighter fresh waters are on the surface unless mixing occurs. In a few places, the land is lower than the ocean, so these areas can capture and contain water, preventing flow toward the oceans. Some water that is absorbed on land helps to recharge groundwater, and some of this may eventually return to streams or the ocean, but some is retained in soils, evaporated or transpired, or retained in aquifers, sometimes for extended periods of time.

Thanks to Dr W.F. Hensen for the answer and also to Dr I. Mandal.

I think this due to the difference in the elevation between land and ocean, as you know Earth consists of continents, shelves, and oceans, so oceans represent the lowest laying relative to the continents.