Michael Phelps was so excited during the men's 4x100m freestyle final he thought his heart was going to "explode out of my chest".
The atmosphere inside Rio's Aquatics Centre spurred Michael Phelps on to claim his 19th Olympic gold medal in the 4x100 metre freestyle relay on Sunday.
As part of the relay squad Phelps secured his 23rd medal with the victory, USA coming home six tenths clear of France in second, with Australia completing the top three.
Phelps produced a fine swim on the second leg of the race after a good start by Caeleb Dressel, before Ryan Held and Nathan Adrian sealed the gold.
"It was crazy," Phelps said of the atmosphere inside the arena.
"I was standing on the blocks while Caeleb was coming in and I honestly thought my heart was going to explode out of my chest.
"Having the amount of excitement, cheering that in the stands during that race, I don't know if I have heard anything like it.
"My last four by 100 relay, it feels damn good to get a win. It was the fastest 100m free of my career."
Rio is likely to be Phelps' last OIympic appearance but he has backed the other three members of the relay team to go on and dominate future editions of the Games.
He added: "The group of guys we have, Ryan swam a great race this morning and came back and swum another one tonight.
"These guys are awesome, they will be there in four years - you got this, I am out."