To determine the timing of the next low tide after a high tide at 6 a.m., we can use the general knowledge of tidal cycles. Typically, there are two high tides and two low tides each lunar day (which is approximately 24 hours and 50 minutes). This means that, on average, high tides and low tides occur about every 6 hours and 12.5 minutes apart.
If a high tide occurs at 6 a.m., the next low tide would typically occur about 6 hours later, which would be around noon (12 p.m.).
Thus, the correct choice would be:
12 noon, because the coastline will turn 180 degrees from the moon.