Water has several interpretations.
It can be seen as a symbol for cleansing, purity, the origin of being (birth water) or calm.
If the water is moving, it can mean energy or energetic movement.
If the water is shallow, it can mean stagnation.
If the water is deep, it can represent the sub-conscious or unconsciousness.
There are even some who are inclined to interpret water as a symbol for sex.
omen
an omen or prophecy
good or bad
No, an omen is a sign, which can mean good, bad, dangerous, etc. And a warning is something that is going to happen. For example the clouds are dark grey, that is a warning that a storm is coming. A omen is something religious and can be and mean different things to different people.
It is a bad omen
to blurtit out
Under favorable omen
Good luck
In Omen of the Stars book 1, beavers build a dam across the river upstream, which causes the lake to dry up.
There have been at least five Omen films. The Omen(1976), Damien: Omen II (1978), Omen III: The Final Conflict (1981), Omen IV: The Awakening (1991) (TV) and The Omen (2006), which is a remake of the first movie.
Omen
It depends on context. "The meteors were an omen of pending disaster" or "the patrol's appearance was an omen of more to come" are both acceptable.