https://www.polygon.com/2018/3/11/17106376/sea-of-thieves-final-beta-open-dates

Sea of Thieves, the massively multipirate online game coming in 10 days from Rare, is staging its last beta. This one, unlike past betas, is open to the general public. The beta is available in the Xbox One and Windows 10 stores for those who wish to play.

The beta requires an Xbox Live account for Windows PC or Xbox One, with Xbox Live Gold required for Xbox One. The beta is underway now and lasts a little more than a day, going to 5 a.m. ET on Monday, March 11.