A massive boat, resembling a floating block of flats, has had people scratching their heads since it moored up in Medway.

The vessel, built originally for the Dutch Navy and which sleeps more than 200 people, has moored on the river at Rochester.

Hillside, described as an accommodation barge, arrived from Portsmouth and is up for sale or available for hire.

Agents Sanderson Maritime, based in Merseyside, were keeping tight-lipped as to what she is doing here.

Wilf Lower, a Chatham-based marine expert, said he had seen similar vessels used as floating hotels or to house an overflow of prisoners.

He said: “I have stayed in a boatel in Amsterdam harbour, but I don’t think she is up to that standard. On the other hand there aren’t any bars at the windows, so I don’t think she is a modern-day hulk.”

Mr Lower said Hillside was more likely here to be used as temporary accommodation for workers taking on a major project or as a “cheap parking space”. He said the barge was probably built in the 1990s and was rebuilt and upgraded in 2004.

She has more recently been used by the Royal Navy in Portsmouth for crews in the process of changing ships.

She is built on three main floors with air-conditioned residential rooms and ample leisure and communal areas.

Brokers Sanderson Maritime writes in its hire details: “Catering can be handled via the well-equipped onboard galley. Further leisure facilities include a bar area and a cinema come lecture theatre certified for 80 people.”

The barge also has a guest laundry.

Rob Gearing, from Medway Navigation Service, which is responsible for movement of ships on the river, said: “We are baffled. We gave a quote for her to come into the river from the sea, but have no idea what she is doing here.”

GPS Marine Services, which operates from Chatham Docks, towed her from Portsmouth on behalf of Sanderson Maritime.

It is thought she could be here for about four weeks.