While reading about (legendary) creature called Mermaid, I stumbled upon 1 of the examples SuvarnaMaccha.

While building Ramasetu, this daughter of Raavana was an obstacle, but later fell in (mutual) love with Hanuman and had an offspring, Macchanu.

This story predominantly appears in Combodian, Thai and some other versions of Ramayana:

When several volunteers have stepped forward Hanuman leads them into the waves. They find a large number of mermaids underwater. As they watch, a new rock is tossed in. The mermaids living underwater take the rocks and carry them away. Hanuman looks for their leader. He spots lovely mermaid supervising the others. He swims towards her but she skillfully evades him. Time and again he begins an attack but it comes to nothing.

Hanuman finds he is falling in love with the creature. He changes his tactics and begins to silently woo her. She responds to him and soon they are together at the bottom of the sea.

Later, Hanuman asks the mermaid why she is stealing the rocks. She tells him that she is Suvannamaccha, a daughter of Ravana (the demon who had abducted Sita). When Ravana saw Hanuman's Vanaras building a causeway he instructed Suvannamaccha to stop it.

Hanuman tells the mermaid why he is building the causeway. He tells her of the abduction of Sita, the battle between Rama and her father Ravana, how they started to build a bridge, and in consequence was ordered to finish the causeway within seven days or pay with his life.

Suvannamaccha turned to Hanuman and her eyes were filled with love. No more, she said, would she prevent Hanuman from completing his mission. Her mermaids underwater would, in fact, return all the stolen rocks to the causeway.

They parted as lovers part but it was not to be the end for them. Hanuman had left a seed with Suvannamaccha and soon she would give birth to their son, Macchanu.

Is this really true?
Do other versions of Ramayanas also recognize Hanuman as Akhanda Brahmachari?