The above paintings, all by the lovely Roberto Ferri, are called Salmacis and Hermaphroditus I-III.
The paintings depict how Hermaphroditus, son of Hermes and Aphrodite, took a detour to bathe in a lake. Suddenly the nymph Salmacis, overcome with a love for Hermaphroditus, decides to seduce the boy into having sex with her. Hermaphroditus nonetheless refuses her, to which Salmacis plots. When it seemed to Hermaphroditus that the coast was clear, he made his move to bathe upon the lake once more, this time without Salmacis nagging him. But out from behind a tree Salmacis sprang and wrapped herself around the boy and pleaded to the gods that they should never part. Her wish was confirmed and the gods mixed the nymph and the boy into what we now call a hermaphrodite.
DO NOT APPROACH RAPACIOUS MERMAIDS.