Sea bathers are in danger of being skewered on rusty metal rods protruding from broken blocks of cement hidden in the surf.
Some regulars at the beach by the Palace Pier in Brighton fear it is only a matter of time before someone is injured by the prongs sticking up out of the sea.
The blocks have been lying in shallow tide by the pier since last autumn when they were ripped away from the groynes during storms.
They pose a serious risk to anyone paddling, surfing or swimming in the sea, especially when they are hidden by rising tides.
Some rusting rods, used to strengthen sea defences, are sticking out at right angles from the groynes just below the tide line.
Children have been seen playing on them, prompting fears they could impale themselves if they fell over or were swept into the metal as they played in the waves.
Henry Law, of Queen's Gardens, Brighton, said: "I have written to the council several times reminding them they should check for underwater obstructions but I've never had an answer.
"They did do some repairs on them last year but they were never finished and they got washed away.
"They should inspect the beach on a regular basis, especially during the summer when there are so many people using the beach.
"But they obviously have not done it at all this year because these have been there since last autumn.
"What if a child fell over on one of the metal rods?"
A council spokesman said: "The groyne near the Palace Pier is called the Albion groyne and is one of only two Grade II-listed groynes in the country, the other being the Banjo groyne in Brighton.
"We did some work on the Albion groyne last year but we will certainly have another look at it when the tide is low and if any repairs need to be done, we'll do them."
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