Beaches in Sussex are among the best in Europe but poor seawater quality still affects Brighton, Hove and Worthing.
New recipients of the coveted Blue Flag awards for good beaches include Bognor and Eastbourne alongside regular winners Camber Sands, Littlehampton and West Wittering.
But in Brighton, Hove and Worthing, water quality remains a bar to the title.
Although it passes EU cleanliness levels it is not clean enough to meet the Blue Flag judges' higher standards.
A Southern Water spokeswoman blamed continued delays to the proposed new sewage plant for Brighton and Hove's disappointment.
But the failure of Worthing, whose inability to meet the necessary standards has in the past been put down to "gremlins", remains a mystery.
Beaches need an excellent standard of water quality to be eligible for a Blue Flag award under the criteria set by environmental campaign group Encams.
The Southern Water spokeswoman said it was good news Worthing had passed a mandatory cleanliness test but said extensive investigations would be carried out to reveal why it had not improved any further.
Bognor's promenade and foreshore manager Barry Welch said a new wastewater pipeline had helped the resort to the award.
He said: "Water quality in the past has let us down - not the standard of the beach, which has been maintained the same way.
"We got a new pipeline to the wastewater treatment works and the water quality has come right up. The Blue Flag is a real feather in our caps."
This year, Blue Flag awards have been won by 122 UK resorts, making Britain the second most improved coastline in Europe.
An Encams spokesman said the UK was eighth in the European table, higher than top holiday locations including Croatia, Cyprus and Ireland.
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