How do I get through this door to Mr. Freeze?

I'm trying to go visit Mr. Freeze for the first time and I can't figure out how to get past this door. I shoot it with my electric gun, but it only opens the door about 8 inches or so. I've tried "rocking" it up and down (does nothing), finding a way to shoot it from behind (no open gap), shooting the nearby camera (maybe someone would come out from inside...but no) and using my remote Batarang (can't find anything to hit inside) to no avail.

Am I supposed to go through this door? I can't find anywhere else to get in.

You should run towards it and when you're close, slide under immediately.

Small gaps like that are too short to crouch under, so you need to perform a running slide.

• On PS3, hold X to run and then press R2 to slide.
• On Xbox 360, hold A to run and then press RT to slide
• On PC, hold Space to run and then press LCtrl to slide.

Pro tip: You can also slide into thugs to trip them up! It's a great way to quickly close the gap on someone who's shooting at you.