Fun and experiments with water - what is your favourite?

We all know that a fight with water bombs or building a water rocket with your kids can be tons of fun.
But what about the things that other people might not even know about?

A water drop generator for example can produce thausands of volts in electricity!
Water can travel up through capilary actions!
Water is even used to break massive rocks in cold climates clean and without the need for explosives!
Even the simple task of freezing water for ice cubes is now a science of its own for most serious bartenders...

One of my old time favourites involving the often weird proerties involved a very small BW TV and a fishtank.
After a lot of cleaning and rinsing I placed a TV into a spare fish tank filled with destilled water.
Some other tiny tanks were filled for comparison with tap water and other household liquids.
Switching a LED on by placing some electrodes in water without a battery was easy to explain as a battery was just created.
Showing that copper can tavel from a wire onto a coin was fun too.
But most people got really stunned seeing a movie or the new play on a TV under water - after all we just learned water and electricity is a big no no...

What is your biggest "trick" or experiment involving water that noone knows about??
I am working on ultrasonic HF/HV experiements trying to figure out why it seems that under certain conditions the water "produces" more energy in the form of gas, steam and light than what is put into the system from the electrical side of things.
Once I can replicate some experiments and understand them I will post my results, so give a few decades please ;)

I grew up in NZ and Guy Fawkes night was something all the kids looked forward to every year. But been a poor kid I often didn't have much money to buy crackers, so a few of us used to make hydrogen with water, salt and a car battery, and blow up coke bottles. It was great fun throwing bottles of hydrogen on the bonfire. I had one bottle take off like a sky rocket, and nearly blew my fingers off when i foolishly lit one with a match. My brother lost his eyebrows when he lit a balloon full of hydrogen, Oh happy days.....