A dino couple's deepest dive

"We should be directly above it, now.", Blimpy commented, shutting off the boat's engine. He and his mate, Cheeks, were out on the ocean in search of an ancient temple that was allegedly on the sea floor around here. The two dinos couldn't afford scuba gear, but were confident they wouldn't need it for this.
Cheeks got up and started doing some stretches. "Still remember those signals we talked about? We shouldn't actually talk down there unless we really need to."
"Think I've got them all. I'm sure we can spend a bit of air on talking, it should be fine. Maybe we could ask a fish for directions, if we're not quite in the right spot." Blimpy grabbed the pair of glowsticks they'd brought, snapping and shaking them before handing one to Cheeks.
The two stood on opposite edges of the boat to keep it from tilting too much, taking deep breaths for a little while. "Alright, you ready?", Cheeks asked.
"Let's go!"
One more deep breath from each dino, and they both jumped into the water, puffing up their cheeks. Neither swam down, letting themselves sink instead, but they still swam to each other to make sure they'd stay close on this dive. Looking up, the surface and boat gradually grew more distant, until disappearing entirely, leaving the dinos themselves as the only things the two could see.
Several minutes passed, and neither Blimpy nor Cheeks were having any difficulty holding their breath, even with their cheeks getting a bit bigger. Blimpy, however, was getting nervous as the sunlight faded, the only light around eventually being each dino's glowstick. Cheeks picked up on his fear before long, and gave him a kiss on the cheek to reassure him.
Finally, after nearly 20 minutes of sinking, they landed on the bottom. Both dinos felt a need to breathe, but it was still manageable for now. Wherever they'd ended up certainly wasn't the temple they'd been looking for, and it wasn't in view either, even after some walking around the nearby area, though it wasn't as if their glowsticks were letting them see very far. Cheeks looked at Blimpy quizzically and waved a finger in a couple circles, doing their signal for "Where should we go?" Blimpy shrugged and pointed off in a random direction, which they both started walking in.
Nothing happened for a while, the dinos continuing to just walk on the bottom and hold their breath. Eventually, they saw a faint light ahead of them that seemed to be moving, and upon getting closer, it became clear that it was coming from an anglerfish's lure. "A-ah...S-so bright...!", it complained, tightly shutting its eyes and trying to cover them with its fins to block out the light of the glowsticks.
Blimpy and Cheeks quickly covered their glowsticks. "Soblrry!", Blimpy glubbed, his bubbling catching the fish's attention. "...You're from above, aren't you? What are you doing down here?"
Cheeks spoke, this time. "Loblokiblng foblr abl teblmple, ibls iblt neblarbly?"
"Oh, it's that way." The anglerfish gestured to one side with a fin, in a direction that the dinos hadn't been going. "I was actually heading over there, you can follow me, but please keep your lights mostly covered."
"Mmhmm."
The dinos followed the fish for quite some distance and time; by the time they arrived, another 10 minutes had passed, and Blimpy and Cheeks' cheeks had each gotten to the size of their head. "I don't know about any other temples, so this is probably it. Good luck with whatever it is you'll be doing in here." The anglerfish swam off, and the dinos were free to finally uncover their glowsticks again.
Even though they were finally starting to have some strain from holding their breath, neither of them were planning on heading back empty handed, no matter how long it took. They set about searching the temple for the treasure, but they weren't having any luck... At least, not with the first floor; it eventually turned out that there was a lower floor. Without much hesitation, they descended.
It was a surprisingly long way down, and Blimpy and Cheeks smiled at each other as they swam, almost laughing at how big the other's cheeks had gotten from holding their breath so long. They took a moment to smoosh each other's cheeks around before continuing, finally reaching the next floor. It didn't seem all that different from the previous one, but they still couldn't see very far, so it was hard to tell.
This floor almost seemed like a maze, with an abundance of turns and braching paths, many of them looking similar to each other. The dinos tried to just go through, but eventually just found themselves back at the floor's entrance, having wasted their time. Blimpy and Cheeks blushed from strain, each with cheeks a bit bigger than their heads, but they still wouldn't be going to the distant surface just yet. What could they do about this maze without a map, though?
Soon, Cheeks had an idea. "Fobllow thble leblft wabll. Itbl's slblow, bublt itbl'll woblrk." Oddly, her cheeks didn't deflate when she opened her mouth. Blimpy nodded at her idea, and the two went back into the maze, taking every left turn they could. Indeed, it was slow; more and more time passed, little bubbles leaving the dinos' nostrils, and soon enough they'd each been holding their breath for an entire hour. Their blushes had turned purple, and they were finally starting to worry about potentially running out of breath... But, they had to be close! It couldn't be much farther to the treasure from here.
It wasn't much longer before the seemingly endless passages changed, opening up into a much larger room with something shining just out of view of the glowsticks' light. Just a few steps forward were enough to reveal what it was: The treasure! Piles of coins, gems, jewelry and what-have-you were all around the room, just waiting for Blimpy and Cheeks to help themselves. They beamed at each other, before remembering the state of their lungs; they didn't really have time to stay here and look for anything especially valuable.
Blimpy grabbed a handful of gems, Cheeks took a gold necklace and tried to wear it but couldn't get it past her huge cheeks, and the two started back the way they came, making sure to follow the right wall instead. They quickened their pace a bit, but the return trip still took longer than they'd like, slowly gaining blue blushes as their lungs started to burn and their cheeks became double the size of their heads.
The dinos whined a bit as they ascended the stairs again, their cheeks wobbling with each step and bubbles occasionally spurting from their squished lips. Neither had held their breath this long before, but they refused to give up, pushing themselves farther and farther as time passed. Getting back to the first floor, Blimpy and Cheeks quickly found their way back outside, and remembered just how deep they were. Being down here so long, they'd gotten used to the water pressure, and had assumed it wouldn't be much longer from here before they'd reach the surface.
Cheeks covered her mouth at this realization, and Blimpy looked over at her in concern. He wanted to kiss her to try to help calm her down, like she had with him earlier, but they cheeks of both of them kept him from doing so. Instead, he rubbed her cheeks with his own, and blubbed a reassuring "Hblang ibln thblere, itbl's jublst stblraiblght ublp, noblw. Wble cabln mablke iblt." Cheeks still wasn't entirely convinced that surfacing was possible any more, but she knew it was at least worth a try.
Both breathless dinos kicked off the bottom and began their long swim to the distant surface. It was a bit slower than their trip down, and was certainly using more oxygen, but progress was being made. Minutes upon minutes, they swam, the blue of their slowly expanding cheeks spreading to even cover their faces. 10 minutes, 20... Just before the 30 minute mark of their ascent, with both of them having been holding their breath for about an hour and 40 minutes, the water around them was finally getting lighter, sunlight becoming visible at last!
Blimpy and Cheeks were both in a rough state at this point; fully blue cheeks and faces, and said cheeks were enormous, nearly the size of each dino's entire body! Even with a fierce burning in their lungs, they still held what breath they had, the light around them giving even more motivation to continue. It wasn't too much longer before the surface was finally visible, the dinos entering the last stretch of both their dive and their breath hold. Over this last distance, it was coming into question which of those two was going to be ending first, bubbles streaming from the dinos' lips and their cheeks partly blocking their vision... Thankfully, the dive was the first to be over.
Their massive blue cheeks partly surfaced before their heads did, and there were two huge gasps as the dinos finally got to breathe again. Panting and continuing to gasp, Blimpy and Cheeks' cheeks deflated and their colors slowly returned to normal over a couple minutes. Still breathing heavily, Blimpy smiled at the gems still clutched in his hand, and after a brief look around to find where the boat was, gave his mate a hug. "W-we did it... H-how long were... Were we down there?"
Cheeks returned the hug. "I-I don't care... B-but I'm glad it was with you..."
After a bit more time to recover, Blimpy and Cheeks started swimming back to the boat. Now that they knew where the temple actually was, they'd easily be able to come back out and claim the rest of the treasure over a few more trips to the seafloor. But, that would be for another day; going off a single breath for so long had been exhausting, and for now, the dinos wanted to return home. Plus, they had to cash in what they'd brought up!