Radak: This was an absolute Chesed of Hashem at the time of creation. He nullified the nature of water to be on the ground, like it was initially, and it [still] is on half the ball (earth). He gathered the water to one place, and the dry land was seen, so living beings and vegetation could be on it. Even though there was a flood, this was only a short time, to avenge Resha'im. Also with this was Chesed to leave [all] species of living beings, and He swore not to bring another flood (Bereishis 9:11). Roka is to put land on top of the water, even though the water was high over the land - "u'Mayim Lo Ya'avru Fiv" (Mishlei 8:29), "Nasan Chol Gevul la'Yam Chak Olam v'Lo Ya'avrenhu" (Yirmeyah 5:22).

Malbim: Initially, the land was covered with the depths. In the land it is possible to return it to void like initially, for its initial creation was covered with water. One must thank Hashem for sustaining it!