Aaero

The thing from the deep (a giant squid/octopus) is on the level called Stigma, the last level of the game. After a quick intro this monster climbs out of the water and grabs onto a big low flying space ship, giving you the opportunity to shoot it. Aim for the head/body and shoot it as much as possible. It will rip chunks off the ship and throw them at you from time to time so be ready to shoot these objects or you'll die and lose trigger time while respawning.

Very soon you'll come to a tunnel, follow the ribbon as precisely as possible as this also damages the beast. You'll then leave the tunnel and get more shooting time. This will be followed by another tunnel with ribbon following. The level then ends. So you need to make sure the beasts health (red bar at the top of the screen) is almost gone before the second tunnel.