Ynys Benlas, Menai Strait
Ynys Benlas is a small, uninhabitable islet of Anglesey found in the Menai Strait at SH549715, southwest of Church Island and immediately south of another habitless rock, Ynys Welltog.
Ynys Benlas in the in middle of that broad but treacherous part of the Menai Strait known as "the Swellies", where the tidal rip can cause the islet to become overwhelmed by the sea.
The county of Anglesey has another islet too named "Ynys Benlas", lying between the Isle of Anglesey itself and Holy Island.