Warning before following the above advice in his video's Consider the following information!Water and hot metal do not mix, it is a more of a BLEVE than an explosion But since water will flash into steam and expand almost instantly to between 1,100 to 1,200 times its volume depending on the books or sources cited.
The warnings about it in a small scale home shop backyard casting,and steam expansion, flinging molten metal. Are very real. In a school shop they had a student that washed the pop cans out and crushed them before they were completely dry insides trapping water inside.
When the water flashed into steam,flinging droplets of molten aluminum everywhere with in about a 15 foot radius of the furnace. The good luck that the students were all down at the other end of the shop 30 feet away, and the emergency gas valve was near the door of the classroom rather than by the furnace. Which at the time was continuing to spit steam and molten metal out as the upper cans melted.
Pouring molten metal in to water, is an old jewelery technique and it is also used to make bead or shot for casting. Most bronze, pewter, lead shot for casting and other work is made this way. Silver shot for a number of granulation techniques are made this way. This a well known and widely covered in most jewelry casting work books.
The problem is your are mixing a number of different statements, Liquids in the material you are melting cans, or oils that are clinging to or inside the material are what will cause the problem. Your results are not the correct ones for the things you are trying to disprove.
That is why the statements about clean, dry scrap or materials for melting are in all the books, and forums dealing with casting.
Your videos are disingenuous in the premise and the results! They are dangerous, because people aren't smart enough to think things through with basic science or physics.
As been said when you pour molten metal into a larger container/mass of water the cooling effect of the water can handle the heat transfer.
If you have ever seen a steel/iron foundry and forming mills in action, you will notice that they use very large amounts of water to keep the equipment and process running.
Also I hope you have continued good luck with that crucible, and it doesn't let go one day as your are pour with a full charge. Since your attire will cause your injuries to be compounded.
You did use a brand new crucible, The point of warming up the crucible and materials in it is to slowly drive off any liquids that may be in the mix and burn off other trash since it expanding at differing rates.
Also the rain part is aimed at not adding wet materials into a crucible, not the heating up to drive off moisture.
The point of the instruction with new crucibles to warm them up again is to drive off moisture that may be in the materials of the crucibles. Since they are compressed from graphite and or carbon materials and a binder, unless they are home made and then are clay based which means they will have moisture in them ( inside the walls of the crucible). Which can cause the water to expand and crack the walls thus leading to failure of the crucible.
Your video's and your statements will be a danger to people that don't better. And I hope no one or your self get injured by your folly and misunderstanding of the process.
The only thing your videos prove is the old adage that" a little knowledge is a dangerous thing!" 
