There is no need to build a sarcophagus around a sunken nuclear reactor. Water is a great radiation stopper, to the extend that you can actually build and opera

There is no need to build a sarcophagus around a sunken nuclear reactor. Water is a great radiation stopper, to the extend that you can actually build and operate an "open" reactor where you can look directly down to the core and see the blue glow from the Cherenkov radiation. It would probably be wise to fence it off somehow.