Movement of fluid in a container filled with that same fluid If a cylinder with the bottom end closed and the top end open was filled with water and then dropped in a pool of water. Would the water inside the cylinder stay in the cylinder? 
 A: You could do this experiment at home. Take a glass of water, add some food colouring und then drop it into your bathtub (fill it first with enough water, otherwise your 'container' will burst...). My prediction:
The water in the glass gets accelerated, first, together with the glass. The glass will then hit the water and will feel a strong deceleration. The water inside it will feel the same, but as a non-rigid fluid the pressure on the vertical axis will get re-distributed to the other sides, particularly to the open top of the glass. This is especially true if your container rotated by 90° while falling. If not, and the top of the glass is still the highest point when landing, then it still holds that there is no counter pressure and the fluid will even out the local pressure terms to get into equilibrium. An additional effect might occur, when the glass sinks deep enough to be covered by water: hydrogen bonds might form and dilute your coloured water with the surrounding water.
Still, I'd like to see the experiment! :D
A: If both liquids, the one inside the recipient and the pool are at the same temperature, once the cylinder reaches the bottom, the liquid near the opening will start to diffuse into the rest of the liquid, but the part at the bottom will mostly stay inside.
While dropping, the liquid near the opening will mix into the pool due to the whirls created in the fall.
Watch out if you use inks to check this experiment as the ink usually has different density than water, and could lead to wrong results.
