Dragon blinked in surprise as Sniffles simply--did it. There was forewarning, but about half a second's worth. He'd expected... discussion, maybe, or questions. But suddenly, abruptly, fatherhood was coming at him again full-steam ahead.
Their cheerful nature was warming, but replaced by a sudden lurch of horror as he realized they were just... shearing off a stone piece right there, while happily drifting there in front of him. He dove without hesitation, catching the shard in his jaws before it could plummet into the Heart's depths.
Then he surfaced in a spray of water, blinking. He tucked the shard of Onyx away on one side of his jaw to speak, maneuvering it carefully with a light toss of his jaws. "I will grant it life on the shoreline," he told them, a little baffled but delighted, too. "Feel free to join me with your stones, if and when you wish. I will build a nest!" he decided. One he could defend, and protect, until the child hatched. "We can both raise the child," he added, though it was almost more of a question; he wasn't sure if Sniffles actually wanted to do that, or really knew how, but he was hardly going to take their stone piece and just leave with it entirely.
He then turned, making for the nearby shore, hauling himself up and into the mud. It took him a few minutes to nudge reeds and muck into a nest; he did so beneath the protective, gnarled roots of one of the mangrove-like trees. Then, gently, he set the black stone into them, and rested his chin atop it.
Let me grant you life, he thought, his imagination wondering just what a mixture of alligator and Oil-snake might wind up looking like.
A moment later the onyx was infused with new fire. Dragon huffed a rumble of approval, then nudged mud over it with his snout--hiding it from sight, and keeping it insulated from the elements.