Question

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.

Answer 1

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.