Dragon Ascendant: Heaven Shall Tremble

Kieran Hale drowns saving someone at the beach where he works as a lifeguard, and wakes up wrapped around a pearl at the bottom of a primordial ocean, hatched into a dragon body nobody in his new clan wants. The elders call him a runt and leave him to die in the abyss. The Dragon Pearl fuses to his core anyway and will not let go. He starts eating the demons that patrol the deep water because there is nothing else down there to eat. Each kill pushes his cultivation up a stage. Over time this earns him a rank among true dragons, level nine, high enough that the same elders who abandoned him start asking what he wants in exchange for standing beside them. The Phoenix Clan moves against the dragons while Kieran is still consolidating that rank. They break through the outer defenses, take dragons prisoner, and hold the clan's numbers down to whatever is left inside the sealed grounds. Kieran goes looking for a way to reverse it and finds that the blood in him traces back further than the pearl, back to the first Ancestral Dragon line. Waking that bloodline is what lets him go after the imprisoned dragons and try to put the clan back together.