"We were just having fun jumping in the water, and some of my friends on the balcony were saying that Nick was under the water, drowning," Reeves said. "I was confused, because I've never seen him get in the water.
Reeves said Williams' sister was able to feel him with her foot.
"I dove in and grabbed him, and I pulled him up," Reeves said. "I got up under him and pushed him out of the water."
One of the mothers at the party got Williams out of the water and started CPR.
Williams was rushed to Scottish Rite Children's Hospital, where he is recovering and is expected to make a full recovery. Reeves said Williams and could go home as early as tomorrow.
"I love him, and I'm glad he's OK," Reeves said.
Williams' family, who are at his bedside, called Reeves their "guardian angel."
Reeves mother said that's just who her son is.
"Kaleb would do it for anyone," she said. "He's got a big heart.