2. The cycle of ebb and high tide is governed by Moon, and twice in a day her water is flowing in and out, as if breathing. When she is straight above or straight down it is the time of flood, her water follows her. This means the times when water recedes are connected with Moon at the horizon in the west or at the horizon in the east.

Picture from Wikipedia where it is stated that Moon returns to the same place in the sky after about 24 hours and 50 minutes, which means the tidal period will be half as long (12 hours and 25 minutes):

... Most coastal areas experience two high and two low tides per day. The gravitational effect of the Moon on the surface of the Earth is the same when it is directly overhead as when it is directly underfoot. The Moon orbits the Earth in the same direction the Earth rotates on its axis, so it takes slightly more than a day—about 24 hours and 50 minutes—for the Moon to return to the same location in the sky. During this time, it has passed overhead once and underfoot once, so in many places the period of strongest tidal forcing is 12 hours and 25 minutes. The high tides do not necessarily occur when the Moon is overhead or underfoot, but the period of the forcing still determines the time between high tides.

The Sun also exerts on the Earth a gravitational attraction which results in a (less powerful) secondary tidal effect. When the Earth, Moon and Sun are approximately aligned, these two tidal effects reinforce one another, resulting in higher highs and lower lows. This alignment occurs approximately twice a month (at the full moon and new moon). These recurring extreme tides are termed spring tides. Tides with the smallest range are termed neap tides (occurring around the first and last quarter moons) ...

Yesterday evening I happened to learn from the Life series on TV that in the extreme south of Africa there are baboons who are living in a tough environment with scarce food resources. They had learned that at the time of spring flood (about every fortnight) it was possible, when the sea was drawing back, to go out among the kelp otherwise inaccessible in order to search for sharks' eggs, a very nutricient food.

I remembered from ika hiku: ... Mermaid's purses (also known as Devil's Purses) are the egg cases of skates, sharks and rays. They are among the common objects which are washed up by the sea. Because they are lightweight, they are often found at the furthest point of the high tide. The eggcases that wash up on beaches are usually empty, the young fish having already hatched out ...

The 'living purses' are far out, but the empty ones are high up on the beach. This makes the image of a shark's egg useful as a symbol which easily can be changed from living (with 'legs') to dead (without 'legs'). We should keep this possibility in mind when trying to understand such glyphs as for instance:

The peculiar idea of chiefs being 'sharks who walk on land' fits with finding empty cases high up on the beach, the inhabitants evidently having moved inlands.