The answer would be tides, due to Earth's and the Moon's gravitational forces between the two planets.The gravitational reaction causes a bulge(water)in the direction of the moon.That's why oceans, bodies of water rise at a certain time of the day, and lowers after a few hours.Without the gravitational pull of these two planets there wouldn't be any waves, that means people wouldm't be able to enjoy surfing.Also the water would be extreamly low, and would take some time to adapt.
