Reflections Off the Waters
It is claimed that when people stood on the boat deck and looked down some said: "You could hardly see the water" and it was just a "black void." Lawrence
Beesley even remarked, "I peered over and saw the sea many feet below, calm and black." So why was it that the lights of the ship were not seen reflected off the
flat calm sea when looking down from decks above, or from a short distance away?

The answer has to do with how light reflects off water.  For light shining almost straight down on the sea, the reflectivity is only 2%.  Most of the light is absorbed.  
The reflection of ship's lights could only be seen from an observer who is relatively far away from the ship, and assuming a flat calm sea. The chart below shows
this.  Only when the angle of incidence becomes greater than about 85° will the reflections be strong enough to be seen with 50% light loss.  This means that any
reflection off of the sea can only be seen from relatively far off.  For a ship the size of
Titanic, with deck lights as high as 70 feet abve the sea, the reflection of her
lights could have been seen at distances greater than about 300 feet away from someone in a lifeboat.  For an observing vessel with height of eye about 50 feet
above sea level, the reflections could have been seen at distances greater than about 450 feet away, almost 1/10th of a nautical mile off, again assuming a perfectly
flat sea.
In his book, The Loss of the SS Titanic, second class passenger Lawrence Beesley wrote:
The mere bulk alone of the ship viewed from the sea below was an awe-inspiring sight. Imagine a ship nearly a sixth of a mile long, 75 feet
high to the top decks, with four enormous funnels above the decks, and masts again high above the funnels; with her hundreds of portholes,
all her saloons and other rooms brilliant with light, and all round her, little boats filled with those who until a few hours before had trod her
decks and read in her libraries and listened to the music of her band in happy content; and who were now looking up in amazement at the
enormous mass above them and rowing away from  her because she was sinking.