You walk over to the small area dedicated to shark costumes, hoping to find an orca costume. Eventually you find one hidden at the back of the rack, although it seems to be too big for you. You decide to give a try anyway, as it's the only killer whale costume they have. It feels like the same sort of material as wetsuit, giving it a shiny appearance, probably to allow the wearer to wear it underwater. Once you get into the changing room, you get the chance to look at it properly. It contains lots of padding, which gives the costume a bulky, muscular appearance, and has a long, thick tail which is also filled with padding. Attached to the neck is a humanised orca head, with white patches around the small eyes and oddly sharp teeth for a costume.
You tuck your legs and feet into the suit, fitting surprisingly well thanks to the interior padding. As you pull it up around your waist, you notice a large penis tucked into a sheath on the front of the costume. Confused as to why a costume has genitals, you decide to tuck your perfectly fitting penis into the pocket for comfort, and pull a drawstring inside the lining to tighten the suit around your waist, and to hold the heavy tail up rather than dragging on the ground. You pull the costume's well-packed arms over yours, and fumble your hands into the large, thick fingers. You manage to grasp the zip on the back and pull it up, making the costume fit perfectly on your body. You admire the large muscles of the suit, thinking that you could easily trick people into thinking that these are real. You tuck your penis-holder into the sheath for decency, and start to pull the solid orca-head over your face. It feels like a motorcycle helmet as you slide it down, allowing you to see perfectly despite the small eyes. You grasp round the back for the zip so you can take it off to pay for it, but can't feel it. As you try to look over your shoulder to find it, you feel your skin start to tingle. Your muscles ache as they suddenly swell out of your body to fill out and replace the padding of the suit. Your concern quickly turns to pleasure as your penis grows as well to match the size of its sheath, an impressive 12 inches. The muscle growth stops as it is on the bring of stretching the costume, now completely replacing the padded fake muscle. You groan as feel your skull crack and reshape to the shape of an orca's, aligning your mouth with the rows of razor-sharp teeth and your eyes pushed out to match the costume.
Cautiously, you raise a heavy, muscular arm and gently stroke your now hugely swelled pecs. The skin still feels like a wetsuit as it did before, but you can feel your touch as if it were your real skin. Going a step further, you pull your new orca-cock out of its sheath, making the new sensitive organ erect immediately from your touch, and you cum all over the changing room almost immediately after rubbing for a few seconds, feeling a brand new sensation of incredible pleasure. Satisfied, you take one last look at the hulking orca-man in the mirror and smirk at your impressive body. You tuck your tool back into its sheath, and walk out of the stall.