Abstract: A vessel for working under water comprising a substantially spherical residence chamber with an atmospheric pressure therein and accommodating necessary monitoring apparatus for controlling working tools and devices arranged on the outside of the residence chamber. The working tools and devices are mounted on a service section to which the residence chamber is detachably affixed by a coupling apparatus actuated from the residence chamber. In case the service section with its working tools and devices gets hooked or wedged during the underwater operation the residence chamber can be released from the service section and allowed to rise to the surface separated from the service section. The working tools and devices of the service section are so designed that in any working positions they do not render the escape path of the residence chamber blocked.