What does this rebus puzzle means ?

What brings you down but never up?

A swan sits at the center of a perfectly circular lake. At an edge of the lake stands a ravenous monster waiting to devour the swan. The monster can not enter the water, but it will run around the circumference of the lake to try to catch the swan as soon as it reaches the shore. The monster moves at 4 times the speed of the swan, and it will always move in the direction along the shore that brings it closer to the swan the quickest. Both the swan and the the monster can change directions in an instant.
The swan knows that if it can reach the lake's shore without the monster right on top of it, it can instantly escape into the surrounding forest.

How can the swan successfully escape?

You have a 12 liters jug full of water. You have two empty 8 liters and 5 liters jug. How can you divide the water into two equal parts using these jugs?

If all Goats are Sheep and all Sheep are Deers, are all Deers Goats ?

Why do you find that most of the buildings are deprived of the 13th floor?

Can you find the mistake in the below statement?

Complete the table series riddle by finding the number that can replace "??".

what's the probability of getting a king or a queen from a pack of 52 cards?

Solve The below Equation:

ALFA + BETA + GAMA = DELTA