Why sea water can not enter and reach to core of earth?

Fluid Dynamics 101 - denser fluid sinks, rarer fluid rises. The density of water is about 1000 kg/m^3. Density of magma (molten rock) is about 2500 kg/m^3. Therefore, water stays on top and magma stays below. read more

On the ither hand, the temperature of the magma in the mantle part of earth is so high that it does not let water in it's liquid state. Tha water is present in the magma only in its molecular state. Due to all these reasons, sea water cannot reach the core of earth. read more

Underwater lava flows reveal that seawater gets cycled to depths within the Earth as great as 2,900 kilometers (1,800 miles), the boundary between the mantle and the outer core. read more

And that’s just to the outer core. If you desire to reach the inner core, you need to drill 3200 miles (5150 km) into the Earth. At this point, you are still not in the center of the Earth. That would require you to drill 3,981 miles (6,370 km) to reach the center. read more