Ocean

The ocean is the only element in this group with mass. Fog and smoke move because the air moves them. Water moves because of what is underneath it, and the frame carries that weight whether the surface is calm or not.

It also removes reference. Open water has no fixed landmark, so a boat has nothing to be measured against except the horizon, and scale becomes hard to judge on purpose.

Swell is the slow movement underneath and chop is the small movement on top. They are separate. A long low swell under a flat surface is a calm day with weight in it, and short chop with no swell is a windy afternoon in a harbour.

The horizon does the work in composition. Where you place it says whether the shot is about the sky, the water or the thing between them, and a horizon that stays level while the camera rolls is the difference between a boat deck and a studio.

Spray appears at the crests once the sea gets up. Below that point the surface stays unbroken, so asking for spray on calm water contradicts itself.

Use it for isolation, for scale, for a journey, and for any scene where the environment does not care about the character.

Skip it when you need a stable frame with a clear subject, because water moves the camera as well as the picture.

Underwater sits below the surface, where light comes down in shafts and everything slows. An ocean shot sits on it. The test is whether the horizon is in the frame.

A lake or a pool has no swell. If the water carries only small surface ripple with no movement underneath, it is not open sea.

Steven Spielberg shot much of Jaws (1975) on the open Atlantic rather than in a tank, and the boat sequences carry a swell that moves the camera as well as the actors.

The sea comes back as a flat texture. Name the swell size, because calm water and a heavy sea are different shots and the model will average them.

The second failure is water that moves like a surface rather than a volume. Ask for the swell to travel under the surface and for the horizon to rise and fall with it.