How do I get through the tunnel below the cryonics room?

There's a creature down there, and it's very hungry.

Of course, you don't want to be the one to feed it.  You're going to have to
look for something else to send down to the tunnel.

Read the monitors on the wall.

The cryofluid in tank 1 is very low.

And if it runs out, the cyberaptor in there will wake up.

Waking up the creature is a good thing, actually.

So open the iris hatch and then drain the fluid with the controls on the wall
opposite to the entrance to the room.

Eventually, the cyberaptor will wake up.  Try fighting it.

After a bit of fighting, you'll get an entry in your journal -- the
cyberaptor seems to have regenerative powers, so you can't kill it.

But you really don't need to.  All you need to do is make sure that it goes
down to the creature in the tunnel.

The cyberaptor is too smart to jump into an open hatch.

But not too smart to stand on the closed hatch.

Even though you can't kill it, you can at least knock it out for long enough
to do something.

If the hatch isn't already closed, then close it.  Then try to get the
cyberaptor to fight you on top of the hatch.