Watch where you step on Waihi Beach, the council has warned.
A rapid drop in the sand level between The Loop and Three Mile Creek has left rocks and rusty metal wire from an old seawall sticking out of the sand, according to the Western Bay of Plenty District Council.
Council reserves and facilities projects and assets manager Scott Parker estimated the sand level had dropped by up to 1.5m in the past couple of weeks, reaching a lower level than it had in years.
"It's happened over a reasonably brief timeframe."
He was not alarmed by the drop, saying it was part of the cyclical nature of the beach.
"The beach is a very dynamic, ever-changing environment."
He suspected recent weather patterns, including big swells that hammered the beach, were largely behind the lowered level.
Mr Parker fully expected the sand to return to more normal levels in due course - as it had after drops in the past - though it was hard to say when that would happen. It could be days, weeks or months.
In the meantime, the council hoped to use the opportunity presented by the low level to remove the newly exposed metal so beach goers would not risk standing on it.
"While they are exposed we can get in there and get the stuff out."
The metal came from old gabion baskets - mesh cubes filled with rocks and used to form rock walls, Mr Parker said.
"These things have been there for decades, covered in sand. The lower level has exposed stuff that we didn't know was there."
Small and large rocks from a rockwall, or revetment, had also been exposed.
"The larger newly exposed rocks in front of the revetment can be used to cover the geo-fabric that is now visible at the base of the revetment. We will also need to remove or relocate some of the smaller rocks."
Other small rocks would be left to be recovered by the sand when the level rose again, he said.
"We hope to get work underway as soon as possible while complying with resource consent conditions."
He said there might be some temporary access issues for beach goers in this area until this work is finished and the sand levels had elevated.