Tides

The Vishnu Purana gives an accurate description of the phenomenon of "tides":

"In all the oceans the water remains at all times the same in quantity and never increases or diminishes; but like the water in a cauldron, which in consequence of its combination with heat, expands, so the waters of the ocean swell with the increase of the Moon. The waters, although really neither more nor less, dilate or contract as the Moon increases or wanes in the light and dark fortnights."