Many special ships, dril rigs, and similar structures share a inconvenient – they do not fit well into the existing ship building and maintenance infrastructure including existing harbors which frequently do not have sufficiently deep access channels. A seastead with deep calm water spaces can be used as service station for afloat repair and building of that kind of structures and draw money from that service. This floating concrete jetty was specificly built to service submarines that share the same inconvenient.