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An artist's impression shows how the surf reef will be made up of 55 sand-filled bags, which will cover an area the size of a football pitch.
The project to build Europe's first artificial surf reef is set to start in Dorset.
The project is designed to double the size of the waves at Boscombe, Bournemouth, but the cost of the scheme has also nearly doubled.
It has risen from £1.4m to £2.35m but is being funded by the sale of land on the seafront to a developer.
The council said the £9.5m upgrade of the area will also boost the local economy by £3m a year.
Actual construction at the site will begin later in the month.
It hopes the regeneration scheme will transform Boscombe, which has been seen as the more deprived end of town for many years.
Bournemouth Borough Council said there were several reasons why the cost of the reef had escalated.
It said it was because it was the first time something like this had been done, because it took longer than expected to get government consent and because the specifications of the reef were changed.
The surf reef - which could attract 10,000 surfers each year to the south coast and is expected to create waves of up to 13ft (4m) - will be ready by the end of the year "at the latest", the council has said.
It will be built with 55 sand-filled "geotextile bags", which will make up a reef covering an area the size of a football pitch.
The bags, which vary in length from 15m (50ft) to 70m (230ft), will be assembled onto a webbing base, which will be taken by barge 225m (740ft) out to sea to the east of Boscombe Pier.