Not safe...

At one end of the beach in 1853 John Candlish (MP) established the Londonderry Bottle works, the largest in Europe; some say in the world at its peak.  It closed in 1921.  At its peak it employed 500 men, boys and women in seven factories in the town.  In full production the works was producing 20 million bottles a year.  

As the massive glass vats were heated up and then cooled the glass set in layers of colour on the lining of the vat and at the end of every day they were hammered to break up the glass off the sides.  This waste was dumped into the sea.  

At the other end of the beach, north up the coast, Sunderland Corporation at that time was dumping household waste into the deep disused limestone quarries above and away from the beach.  Over the years the limestone cliffs eroded and the waste in the quarries fell into the sea.  Now 100 years on there is a plentiful supply of sea washed glass of all shapes, colours, origins and sizes and each tide reveals a fresh supply.

Indicative of the geology along this coast are these limestone caves at the north end of the beach.  Explored by hordes of children in the summer, today they are deserted.  Personally I won't go in them anymore, even in my time round here some have collapsed but these have been around for 50 years that I know of.