Looking for 2000’s game for kids – played as an animal avatar

Hi, I have this game stuck in my mind but I cannot for the life of me remember what it was called

– I'm pretty sure it was online from the late 2000's

– I remember that your avatar was a 3D animal model (possibly a bear, I believe it could be switched out for something else? not too sure) and you could move around a map that was 2D

– one of the maps featured a submarine and you could go through it, and there was another bear that you could get little quests from

– for some reason you were also able to become smaller or bigger at random points, not sure why, probably to crawl through spaces

I know that's not a lot to go off of but if anyone has any ideas please let me know!