It reads like the beginning of a script for one of those giant-aquatic-monster summer movies starting, say, Jason Statham.

Quoting from the OP: "The seabed 'observatory', worth about €300,000 (£270,000), weighed more than half a tonne. It could not have been dragged off by a storm ... Divers only found a torn power cable at the site, 22m (72ft) down and 1.8km (1.2 miles) offshore."