Environment - Infestation

Story of environment:  In the future there are urban places that are abandoned by humans. But still there are life forms that take these places for themselves as a home. Main area is meant as some kind of metro station, but as it is left ruined over time, it is also partly flooded. So large part of objects and path ways are submerged in water. A perfect undisturbed place for a strange life forms. The creature itself is not evil nor good, but the caution is needed as it can defend itself by thin and very long wire like tentacles.