It totally is a reboot and not a 4th movie that happens to be completely unrelated to the other 3.
First things first:
Damn, Bindi sure looks a lot like her late father. Seriously, I see a gender-bent Mini Steve when I see her. With her joyous reaction next to the animals (when they're not using a CGI whale, she oozes that Steve Irwin charisma.) Whoever's dating her dodged a massive bullet... Could you imagine how awkward it would've been meeting Steve and he'd do the threatening father routine to protect his little baby girl. He'd ask you to help him wrangle a crocodile. He'd do the usual Crocodile Hunter thing while casually describing how he'd make you disappear.
Second: Beau Bridges is playing another dad here... (OK he's a GRANDdad, but after being Fred Savage's dad, Christian Slater's dad, Jonathan Brandis's dad makes me think that he's the go-to movie dad...)
Third: Bindi was like 10-12 when this movie was made and acting isn't that great... doesn't help that the movie is a bad rip-off of the original Free Willy.
Fourth: The movie is ASS! DON'T BOTHER!!!
I only got it because it was like $5 and it had 2.5 Good Free Willy movies.
Fifth: Bindi is all grown-up now and she competed in Dancing with the Stars...
Seventh: Did I mention the movie is absolute crap?