The water in the tender coconut is actually:

The correct answer is Option (2) → Free nuclear endosperm

Option (2) Free nuclear endosperm — Correct. In coconut the primary endosperm nucleus divides many times without cell walls forming, so the endosperm is free-nuclear. The water of tender coconut is this free-nuclear endosperm, made of thousands of nuclei; the white kernel around it is cellular endosperm.

NCERT Extract:
Endosperm – “… In the most common type of endosperm development, the PEN undergoes successive nuclear divisions to give rise to free nuclei. This stage of endosperm development is called free-nuclear endosperm. Subsequently cell wall formation occurs and the endosperm becomes cellular. The number of free nuclei formed before cellularisation varies greatly. The coconut water from tender coconut that you are familiar with, is nothing but free-nuclear endosperm (made up of thousands of nuclei) and the surrounding white kernel is the cellular endosperm.”