In another photo, Chandler can be seen holding the crocodile down, while his other half measures its length.
'Here's another shot from my first croc jump! By far the most amazing feeling in the world. Can't wait for more!' Chandler wrote.
Bindi, 18, revealed in July last year she was in a relationship, but stayed mum on who the lucky guy was.
'There is someone special in my life right now, and I'm really happy with that,' Irwin told Entertainment Tonight.
Despite attempts to keep their relationship private, Powell posted a picture with Bindi wishing her a happy 17th birthday, claiming to have swum the croc pond.
'Happy Birthday to this gorgeous girl! Feel very blessed to have you in my life. Counting down the days until I get to see you again! @bindisueirwin#TotallyGushing #ILoveCamping#ILoveTheOutdoors #ISwamTheCrocPond,' he wrote.
The croc pond reference was the only confirmation fans needed. Bindi’s late father Steve Irwin previously said anyone who wants to date his daughter must first swim across the croc pond.