Tian Yu's dragon form recieved the full impact of the explosion. As such close proximity, the brunt was quite strong and disrupted whatever protective aura was shielding him from the quicksand and knocked him right into it.
The atavistic dragon form cloaking him did not completely shatter, but its aura waned visibly. Tian Yu was not concerned about that as he sunk, he was more worried about Yao Houyi's next action.
