Yay, more of this! Okay so I'd definitely do it like the others (I'm always late to the party):
First cut off the movement, then if it doesn't turn around to go up and out immediately, freeze the bitch, and if it starts doing funny business, get naked and throw it tf away.
And by throwing it away I mean try to get it off and then examine, but if it slithers away don't run after, and if it slithers closer, just keep a distance.
And lastly orientation I can't help since I'm already completely lost.
If you could add labels to the different tunnels it would be easier to keep track of. ^^ But anyway I'm against things that are submerged, not only is it dangerous because "they" (whatever is in there) have the home advantage, it's also plain disgusting to swim in sewer water.