The 57.5-million-euro concession agreement to use and exploit the marina of Alimos, in southern Athens, for a duration of 40 years was signed on Wednesday with Aktor Concessions.
The value of the agreement amounts to at least 177 million euros, including an up-front fee, an annual concession fee and a revenue-sharing expressed as a percentage of the marina's annual turnover.
Greece's tourism industry hopes that overseas lockdowns will continue to ease and flights can begin to pick up shortly.
The government is focusing its efforts on attracting European visitors, and counting on Greece's success so far in containing the epidemic to reassure visitors that they will be safe.
Greece's tourism sector hopes to be "open for business" sometime in July, Tourism Minister Haris Theoharis said in an interview with BBC on Thursday.
Asked how soon Greek borders may reopen, Theoharis said that this issue will be discussed with health experts but the country hopes to "salvage" most of the summer season.