Waterhouse was a professional artist who produced more than a hundred paintings in the Pre-Raphaelite style and was well-known and respected by the public and his peers. Waterhouse was born in Rome in 1849 and studied at the Royal Academy Schools in England. The quality of his work is without question.
The theme of Hylas and the Nymphs is one which might arouse disapproval or even hostile rejection by some parents or caregivers. Hylas is being tempted by the nymphs in the water, though the painting as an independent image does not specify whether or not Hylas submits to the seduction. One could apply different points of view to the depicted situation (which is really how art should be viewed: fill in your own take on it).
The partial nudity, though it is, in my opinion, quite modest, might also be found objectionable. These days we must not fail to consider that others can be very picky about such things.
Chapter 167.080 outlines the limitations set on displaying of such imagery to minors. I would assume that legislature in other U.S. States is very similar on this matter.
Waterhouse's painting "reveals a person or portion of the human body that depicts nudity," and could therefore be subject to legal guidelines. The judgement call as to whether or not Waterhouse's painting is "obscene" is largely up to you.