Which preposition to use with tortugas

to Occurrences 1%

The second is called los Organos; and the third los Martyres, which are next the shore of los Tortugas to the westwards; which last being all sand, cannot be seen at any distance, wherefore many ships have perished on them, and all along the coasts of the Bahama channel and the Tortugas islands.

under Occurrences 1%

Brought to off Tortugas under our foresail, and about 5 A.M. saw a sloop bearing down upon us.

Which preposition to use with  tortugas