Fans took to the comments to remark on the swimmers' relationship.
"You’re the best Ian! Looks like you’re being a great mentor too," one penned.
"The GOAT and his protege. Go Cody!" cheered on another.
Even Cody shared his own cheeky comment: "Beard on point."
The Head Above Water documentary follows not only Ian and Cody but also champion swimmers Bronte Campbell and Kyle Chalmers as they prepare for the 2021 Tokyo Olympics.
In the trailer, Cody, who famously dated Miley Cyrus, is pushed to his limits but Ian slams claims that the singer's move into swimming is a publicity stunt.
"There are going to be people who do not like Cody and what he's doing and most of that comes out of jealousy," Thorpie said in the trailer.
"I've seen Cody's level of dedication to this. Cody in the backyard pool doing laps on what we call a bungee cord or a tether, by himself just getting better and better each week," he remarked.
"I knew that he was serious about it, I also know what he was able to do when he was a young swimmer and so knew that there was a prospect that he'd be able to get back in and swim well."
Both Cody and Ian have spoken publicly about managing their mental health as well.
“I was rebelling. I just burnt through everything possible, really quickly. And I’m really glad about that, actually, because I kind of got through it.”
In the Head Above Water trailer Ian, who has openly discussed his battles with depression, described his darkest days and will no doubt be a mentor for Cody in that light as well.
"You have something that is so consuming of all of your life and then all of a sudden it isn't there. It was dark, it was as dark as it gets."