After checking the list a few times and failing to find anything she fancied over the default option, Rachel decides to ask the receptionist directly, "I beg your pardon, but among the later options I can ask over... are mermaids included".
"By determinism you mean merfolk, yes we do offer it. Only concern is that, as a dual mythology/marine option all guests who choose it must be taken to a different transformation section below the buildings" the receptionist answered.
"Can you escort me then?" Rachel requested, "...alright... please follow me" the receptionist agreed before leading Rachel off.
A while later in the somewhat flooded linking basement of the transformation buildings, "like with normal marine guests it is forbidden to leave the legal area of the island whilst transformed... also their will be a little discomfort once injected" the receptionist explained as she returned with an injection needle,Rachel having already stripped naked as in her opinion mermaids were meant to be so and had been waiting for the process to start.
The moment the serum was injured into her body Rachel felt herself feeling oddly trickled, both all below the waist and around her neck, only to then suddenly fall down as her legs refused to hold her up.
leaning on her elbows to see what was happening, Rachel was awestruck by what she witnessed, her legs were rapidly melding together into a single limb while her knees and ankles were absorbed away, her toes expanded in great length and spilt in tiny branches, before finally silver scales formed all over her new tail and her breasts while a gray membrane formed between the toe branches to create a tail-fin.
"thanks... i'm sure she'll be glad" the receptionist suddenly said through this transceiver before redirecting her attention back to Rachel "Miss Sinclair, a guide has arrived to escort you to the rest and meeting area for the merfolk outside the transits tunnel".
"thanks you" Rachel thanked as she entered the water, "oh one more thing, please let the guide know if your claustrophobic" the receptionist then instructed, "i'm not, why though?" Rachel inquired, "merfolk sleep inside these giant clams normally, but we have arrangements for those with claustrophobia to have alternative sleeping arrangements" the receptionist answered, "oh I see" Rachel responded before diving down and swimming off.
Once below to water line Rachel felt the perfect feeling of the water passing through her body like air, or maybe her body could now metabolize oxygen from the water, it currently didn't matter as she swam out to meet the guide.