A very strange twisting feeling takes over your nether regions. You can feel flesh reshaping, holes fusing, penile tissue growing and ... splitting? The warm salt water is still caressing those parts pleasantly through it all, too. All of these sensations happening in such a sensitive area makes you close your eyes and groan a bit. Opening them again, you're very curious but also a bit afraid to start looking down and messing with your manly parts in front of a strange woman. Instead, you just bite your lip and look tense for a second or too.
"I feel funny," you manage to say after a while.
"I should think so!" she giggles.
Curiosity is getting the better of you, so you start subtly exploring a little bit. You put your hand behind your back as if to scratch and then very discretely try to feel your butt. You can't find it: your hand can't feel any asshole, or even a buttcheek back there. Remembering the sense of a couple of holes coming together near your crotch, you finally through your caution to the sea winds and look down. You gasp, flinch, and flail backwards in the water for a second. "What the--?!"
Your balls are GONE, and you can see a long, thin slit under where your belly button used to be. (You don't have a belly button anymore! Unless that slit IS your belly button?) That's not even the weirdest part, though: sticking of the flesh just underneath your slit, you can see a pair of long, sausage-like, slightly pointed bulges pointing straight down toward your legs. What could those be? Grabbing onto one of them, you shudder in sexual pleasure. Remembering the splitting feeling within your cock, you grab the other one and moan. Letting go of either protrusion is going to be hard, but you have to satisfy your curiosity about your new slit. Cautiously slipping a finger in there, you twitch and shiver, trying to make sense of the feeling that you've managed to stick a finger up your urethra AND your missing asshole.
"Sharks are arranged quite differently down there, aren't they?" says the genie with a smirk. Remembering that you aren't alone, you force your hands away from your new arrangement. You do permit yourself another decent look at what you possess now, already missing the pleasant stimulation on your claspers. A sudden warm surge out of your slit into the seawater surprises you, and then you blush at the thought that it almost felt like peeing in the pool. It might take a while to get used to doing that through a cloaca instead of a penis. You might as well get used to doing it wherever you happen to be, though, since you'll be drinking, breathing, and dirtying the same water forever if she's really turning you into a shark.
A sudden pressure on your legs distracts you, and you look down further to see your legs shrink. You aren't sure whether it's an optical illusion in the water, at first, until you see and feel your feet changing as well. You can't move them as much, thanks to the skin fusing and bones shrinking. It feels as though someone is squeezing your legs like an empty roll of toothpaste, but it isn't really painful as such. It certainly looks as though it should be painful. Soon your legs are so small that they don't even dangle past your torso anymore: they're just sprawled out from your crotch, mainly toward the sides rather than straight down like your claspers. At last, you get to watch them flatten and flare out into triangles until they look more like crotch fins than a pair of legs. That's it! They ARE crotch fins, or rather pelvic fins... shark fins! You grin widely and give a mischievously enthusiastic look to the genie. You almost can't wait for whatever's next.