The death is the fifth since 1984 on Key West's 10-mile triangular course.
In 1963 she claimed the women's world record for speed over a 500km triangular course of 103.33km/h.
Divisions 1 and 11 use a conventional triangular course for all their competitions.
A series of triangular courses for the different classes have been brought into calmer waters.
Swimmers will swim in a clockwise direction on the triangular course.
The wind had increased to 15 knots by the upwind mark, a point 13 miles from the start on the triangular course.
By radio, the crews agreed on a triangular course with equal legs of about eight miles.
Most of the fleet competition schedules call for seven races, one each day on a triangular course of 8 to 13 miles.
The last part of the Challenge was a maximum speed trial, on a 297 km triangular course.
The second race is scheduled for noon Friday local time on a 39-mile triangular course.