Does eating half of a juicy watermelon meet the required amount of water for a day? ?

the watermelon is roughly 14.8 in. from one pole to another and the diameter of the equator of the watermelon is roughly 7.5 in.

The recommended daily fluid intake depends on your weight, your
activity level and the temperature and humidity of your environment. 

The old rule of 8 glasses of water daily is a good average of the recommendations.

(8 glasses = 64 fluid ounces = 2 quarts = 1/2 gallon)

For the watermelon . . .

The volume of an ellipsoid (squashed sphere) =

     V = (4/3) (pi) (polar radius) (equatorial radius)²  =

           (4/3) (pi) (14.8 / 2) (7.5 / 2)² =

           (4/3) (pi)    (7.4)     (3.75)² =  436 cubic inches  (rounded)

436 cubic inches =  241.5 fluid ounces = 1.89 gallons (rounded)

1/2 juicy watermelon = 121 fluid ounces

We won't get into what percentage of the juicy watermelon is water.

If it's anything over 53% water, than half of it gives you your
recommended daily intake of fluids. 

I think we can pretty much rest assured that a juicy watermelon is
more than 53% water.