Peace and quiet on the open seas.

The most striking feature of Perini Navi’s Grace E is its sundeck, which was designed as a health spa at the request of the owners; they wanted the 240-foot trideck super­yacht to be a spa at sea. The designer Philippe Briand accommodated that request by outfitting the 2,500-square-foot space with a hydro­therapy room that includes a cold plunge pool, a meditation room that features a 180-degree view of the sea, and a massage area that is connected to a hammam-style steam r…