What brings you down but never up?

A man fell off a smuggling boat into deep water. He could not swim and he was not wearing anything to keep him afloat. It took 30 minutes for the people on the boat to realize someone was missing. The missing man was rescued two hours later on the return trip. Why didn't he drown? Note:- He didn't know swimming, the sea was deep, and He wasn't holding anything

What work can one never finish?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

I shave every day, but my beard stays the same. What am I?

I have 50 feet long of cloth, I need to create 50 handkerchiefs each size of 1 foot. I take one minute to cut a 1-foot handkerchief. So how long will it take to cut 50 handkerchiefs?

I know a nine-letter word having only one vowel.
Do you ?

You have a basket containing ten apples. You have ten friends, who each desire an apple. You give each of your friends one apple.
Now all your friends have one apple each, yet there is an apple remaining in the basket.
How?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

Decode below rebus
D
N
A
T
S , D