Complex sentence: He disappeared in November 1909 while aboard his boat, the "Spray", originally sloop-rigged, but re-rigged as a yawl in the midst of his circumnavigation, while Slocum was traversing the Strait of Magellan.
Split into simpler sentences: He disappeared in November 1909 while aboard his boat, the "Spray". The "Spray" was originally sloop-rigged, but was later re-rigged as a yawl in the Strait of Magellan.