Sploosh
You zoned out for a bit. You barely perceived how long it took to slip down Cynthia's throat. Now you're swimming in her tummy. You look up, and see the entrance to her stomach sealed shut. In any other creature, you'd be frightened, but this is exactly what you want.
Bloop
That's why you wanted to be eaten in the first place. The bubbles full of thick pink smoke float to the surface and burst. You swim over to one and take a deep breath. Your body curls up from the sheer pleasure. You feel incredible. It's like the pleasure you feel is doubling every second. You'd die for every whiff. Luckily, you don't have to. Not yet, anyway.
Your surroundings are really setting in. Cynthia's stomach is dripping with slimy digestive juices. The bones of her previous prey float around lazily, swished around by her gastric motions. Your body feels like it's... becoming less solid? You're not sure what being digested is supposed to feel like, but this feels pretty inconsequential.
It's so warm. So cozy. So... orgasmic. You let yourself float to the top of the bubbling, gurgling acid. The pink gas is starting to accumulate. Getting hard to see. You take a deep breath. Ohhhhh yeah...
Cynthia's gut is a pleasant cacophony of gurgles, bubbling, churning, and squelching. It's very loud, but it puts you at ease anyway. You feel your eyes closing, as the exponential growth of heavenly sensations continues. No, that's the wrong word. Heaven is hell compared to this.
Your enormous predator says something, clearly mocking you. "Have fun in there~"
She knows you're slowly digesting inside her, bent completely to her will.
You don't care.

...

Several months pass, bathing in digestive juices in this giant shark's belly. The euphoric pink mist has made you feel better than you could have ever imagined and then some. Every moment is orgasmic beyond comprehension, and with every breath it doubles in intensity. Your limbs turn to sludge, one-by-one. You can feel your doom impending, creeping. You're still content with your choice. Best decision you've ever made, as far as you care.
Eventually your body is just barely clinging to life. Each breath becomes more difficult. You're dying. It was worth it.
You take your last euphoric breath, completely absorbed in pure pleasure, and are completely digested in Cynthia's stomach.