Even with the grate, the tunnel to your right offers a closer escape route. You inch along the wall towards it.

You slink towards the opening on your right, keeping your eyes on the worm the entire time. Thankfully it isn't long before you can duck into the tunnel and begin wading towards the grate at the far end of the tunnel. Torch light filters through the rusted bars and reflects off the water, casting strange shimmers over the stone around you. Near the torches is a stone stairway leading up and out of sight. The grate itself is unfortunately locked, but it's possible that you could disengage the lock with enough time...

A soft splash behind you catches you off guard. Whipping around, you can no longer see the worm. That can't be good... did it spot you? So much for having time - if it's headed your way, you definitely can't risk unlocking the grate now. Looking around for some sort of escape, you notice another, smaller opening to your left - it's completely cloaked in shadow, so it could be a good hiding spot until the worm leaves. You also notice an underwater opening in the grate's bars; it might be large enough to squeeze through and get out of the worm's reach. Time is of the essence.