You can lead a horse to water, but if it’s wise, I think,
until you’ve added malt and hops, you cannot make it drink.

When my mother read my post Menagerie (Part 1) she reminded me of this facetious version of the well-known saying.  Do horses really prefer beer?

Water down
means dilute and can be used figuratively.

Pouring oil on troubled waters
is a way of making the waves smaller.  As long as the oil floats on the water it could be helpful.  There have been too many disasters worldwide where enormous quantities of oil have been accidentally spilled.  If someone tries to help reconcile others who cannot agree, they may be pouring oil on troubled waters.

Don’t throw the baby out with the bathwater.
sometimes things or systems need to be reorganised.  This ought to result in an improvement unless the object of the change has been forgotten, in which case the baby might have been thrown out with the bathwater.

I feel it in my water.
Our bodies are mainly water, but when people refer to their water, they usually mean urine.  It is an expression used when people have a feeling that something is going to happen.

Take more water with it
is advice given to someone who stumbles, whether they have been drinking alcohol or not.

Come hell or high water.
Whatever happens.  High water is another expression for high tide, but some tides are higher than others.

Water finds the lowest course.
This is true.  Liquids do not flow uphill without a pump.

Waterfall

Waterfall

Watertight.
If something is watertight it does not leak.  If an argument is watertight, no-one can find (or pick) any “holes” in it.

Still waters run deep.
This is a proverb about quiet people having profound thoughts.  In a river there may be deep pools where the surface of the water is undisturbed.

If someone has an idea others might try to discourage them from acting on itPouring cold water on it is an appropriate idiom here.

Skating on thin ice.
Anyone who has read “White Boots” by Noel Streatfield knows how dangerous it is to skate on thin ice.  Sometimes a person’s actions or words can be as perilous.

The tip of the iceberg
is the part which is visible above the sea.  As a metaphor it is the first part of something which may turn out to be much bigger.

Letting off steam
is a way of reducing pressure from a boiler, for instance.  People need to let off steam too.

Steam locomotives have to get up a head of steam before they are ready to go.  A head is a measure of the pressure.

If someone is very angry he may be said to have steam coming out of his ears.

Water, ice and steam are the liquid, solid and vapour states of the same compound H2O.  It is an amazing substance, essential to life on earth and it has properties unlike any other substance.  For example, when it is cooled down towards its freezing point, it reaches the anomalous temperature of water at which point it has its maximum density.  (4 degrees Celsius)   On further cooling the molecules begin to arrange themselves to form the crystalline structure of ice, which is less dense than water.  The fact that ice floats on water is crucial to pond-life.

In the Gospel of John Chapter 4 verse 14 (NIV) Jesus tells a Samaritan woman “whoever drinks the water I give him will never thirst.  Indeed, the water I give him will become in him a spring of water welling up to eternal life.”