If we assume Sun must leave 'earth' in order to fly over the 'water' (the 1st quadrant in the picture above) it resembles how Sun during the nights has to travel under the earth in order to reemerge in the east in the morning next day. When he is down in the underworld his light cannot reach us and it is night. With water above it is hard to see anything.

But there is a major problem with this view of cosmos, because Sun's path will then be abruptly broken off both at Sagittarius (Cargo Boat and Pabilsag) and at Gemini (Great Twins). A more natural way to travel would be for him to follow either the Milky Way or the ecliptic, not to change direction like this.

I guess such a consequence of the precession of the equinoxes, which in the future would move spring equinox into the 'sea' (Pisces) - of course foreseen already by the ancient Babylonians - demanded a solution. Sun must be given a hand to enable him to cross the 'water'. A possible way could be to have him 'killed' at Sagittarius and then to have his living spirit transported by a bird (Eagle & Dead Man) past the dangerous area.

Another solution would be to give him a 'talisman' fetched from the golden era when spring equinox not yet had been 'inundated'. Such an object could be for example the dry old bone of a horse (or some other land animal with 4 legs). Looking around for a suitable such old bone the jaw of a horse would be found fitting, with 24 teeth for chewing corresponding to the 24 halfmonths in a year.

The 'cup' part of the old horse's head would be an ideal symbolic object. Not only would it have the correct number of teeth but it would also allude to the opening of the 'jaw' between sky and earth at spring equinox.With such a jawbone it would be safe for Sun to go on moving along the ecliptic also in winter.