Name of this early 90s movie?

I watched it when I was a kid in the late
90s early 00s:

Kids walk into a sewertype place where they have to walk over a vortex
tube - a metal railing surrounds it. They fall in trying to walk over
it on a plank and they enter another jungle-like world with odd
reptile type people who I THINK were animated. The kids were real
actors though.

I HOPE this isn't too vague... Thats all i remember. hopefully someone
will recognize it. It was also pretty bad haha