"Help me... with what?"
"Getting in touch with your feminine side." They said in a melodic tone before beginning to gently hum.
Falling somewhat back into a trance, you allow them to lay you on your back where they proceed to run their hands through your hair. With each pass of their fingers, your hair grew longer and longer until it was long enough to cover your butt were you standing up.
While you were aware of their actions, you were unable to process the results. This continued as they rubbed your face and body, as if to wipe away all your hair like a sponge removing residue from a frying pan.
The gentle rubbing changed to a more forceful massage, further smoothing your body and even reshaping it. First your face was made rounder and more beautiful; next, your neck was narrowed and your adam's apple was squeezed to almost nothing. The gasp and soft moan that resulted from your sharp breath of air was much more feminine, but you still could not put two and two together. The mermaids then started squeezing your arms into a slimmer size, followed by your hands. As they pushed your shoulders and waist inward, one of them put their hands on your chest. She cooed in delight as she, and you, felt your breasts swell in her hands. They stopped at C-cups with just the right sized nipples, perked up from the ocean breeze playing off their dampness.
Between the massaging and the beautiful humming, you were starting to get rather aroused, but somehow, the mermaids managed to gather your "personal effects" and slowly push them inside you, pulling your hips out to make room for their new function. Finally, they bowed your legs outward to complete your feminine curves before working the same magic on your feet as they did your hands.
Once they ceased their humming, your attention returned to 100% and you saw the fruits of their labor.