First Phase is eight weeks long and emphasizes increased physical conditioning forstudents, including weekly 4-mile (6.4km) runs in boots as well as timed obstaclecourses. The student will also take part in ocean swims of up to 2 miles (3.2km) whilewearing fins. Rudimentary training also includes classes on basic small-boat skills. Theinitial four weeks of First Phase are preparation for the fifth week, commonly known as“Hell Week.” Students undergo five and a half days of continuous training, with no morethan four hours of sleep during the week. Hydrographic surveying and the preparationof hydrographic charts are taught over the remainder of the BUD/S First Phase.