Swimming (part of) the Atlantic
She arrived in Trinidad on February 5th from the Cape Verde islands (off the coast of Africa), having covered 2700 miles in 24 days. That is equivalent to 112 miles per day or an average of almost 5 miles per hour. Since even Michael Phelps at full sprint covers only about 5 miles per hour, Jennifer's swimming trip obviously included substantial time on board her support catamaran.
The prior "swim across the Atlantic Ocean" by Bernard Lecomte followed a similar swim/boat format. Lecomte averaged over 8 miles per hour in his transit. Nonetheless, both crossings are impressive endurance adventures.
(Hat tip to Roman Mica)