Tidella

Meet Tidella, the ocean stretched into two bulges by the Moon's uneven pull.

The Moon pulls on every part of Earth, but more strongly on the side facing it and less on the far side. What raises tides is that difference. Relative to Earth's centre, the near-side water is pulled toward the Moon and the far-side water is left behind. That makes two bulges, one facing the Moon and one opposite. As Earth turns under them, most coasts see two high tides a day.

The difference in pull across a body of radius r falls off as 1/d³, not 1/d², so distance matters a lot. That is why the Moon, though far less massive than the Sun, raises tides about 2.2 times larger. When Sun and Moon line up, at new and full Moon, their effects add into larger spring tides.

Tidal friction slowly lengthens Earth's day and moves the Moon outward, by a few centimetres a year.

Real tides depend strongly on coastline and seabed shape. The two-bulge picture is the equilibrium idealisation, and actual tidal ranges vary from almost nothing to over 15 metres.