Water naturally moves via the passive process of OSMOSIS, which is the movement of water from a region that is less concentrated to a region that is highly concentrated via a semipermeable membrane.
In this question, there is said to be a net movement of water into a cell from the surrounding tissue fluid. Based on osmotic principles, this means that the solute concentration of the tissue fluid is lower than that of the cell. Hence, the tissue fluid contains more water, causing it to move towards the cell.
