Penarth Marina has lost its Blue Flag status in this year's Wales Coast Awards.
It was the last remaining site in the Vale of Glamorgan to retain the prestigious worldwide status, which recognises excellent water quality and facilities.
The privately-owned marina had been recognised since 2021.
Six beaches across the Vale secured the 'Seaside Award', a UK-only scheme which recognises "clean, attractive and well-managed" stretches of the coast.
They include Southerndown, which was stripped of its own Blue Flag status in 2023 because of concerns over its toilet facilities.
Five locations - the Cold Knap, Col-huw in Llantwit Major, Jackson's Bay, Penarth beach and Whitmore Bay - retained their Seaside Award status from last year.
Last year, Dunraven Bay was given an 'excellent' grade for bathing water quality along with the Knap in Barry and Col-huw while Penarth, Jackson's Bay and Whitmore Bay were deemed 'good'.
This year, 21 beaches and marinas were awarded Blue Flags - down from 24 last year - while fifteen sites secured the Seaside Award, up from 12 in 2024.
13 sites retained the Green Coast Award, recognising excellent water quality and unspoiled environmental areas.
Owen Derbyshire, chief executive of Keep Wales Tidy, said: "Most people are familiar with the Blue Flag and Seaside Awards – but it’s just as important that we recognise the wild, unspoilt beaches that stretch along so much of the Welsh coast. "
"The Green Coast Award signifies the highest standards of water quality, environmental education, and site management. These are the sweeping coastlines that define Wales on the world stage – and it’s right that we celebrate these extraordinary places."
Keep Wales Tidy says the annual awards play a vital role in protecting the marine environment - and signfify that a beach or marina meets and maintains the highest environmental standards and achieves tough water quality targets.
Deputy First Minister, Huw Irranca Davies, added: "Wales boasts some of Europe's finest beaches and water quality, and the global recognition of our coastline is a true reflection of the dedication and hard work of so many people...I commend the dedication to preserving our pristine coastal environments."
"As we celebrate in this achievement, let us also heed the call to protect and preserve our coastal treasures. Let's ensure that we leave nothing but footprints, allowing these breathtaking spaces to be enjoyed for many generations to come."
Vale of Glamorgan Council has been approached for a comment.

Hepatitis A Vaccination Programme Launched for Young Children in Barry Amid Ongoing Local Cases
Barry Councillor Urges Local Chapels to Help Update Wales‑Wide Heritage Project
Dispersal Order issued at Cosmeston as council warns of ‘extremely dangerous’ behaviour
Three Rescues in 24 Hours as RNLI Barry Dock Urges Caution Around Sully Island
Police Investigate ATM Theft in Cowbridge After Pensioner Targeted
Break‑In at St Athan Community Centre Forces Volunteers to Divert Funds from Upcoming Events
Vale Students Celebrate Strong A and AS Level Results
Llantwit Major School Celebrates Record-Breaking A Level Success
Senedd recess: What have the Welsh political parties been up to so far?
Vueling withdraws winter flights to Aicante this winter
Playground in Barry forced to close after fire damages equipment
Campaigners Take Fight for Fairer Pathways in Welsh Women’s Football to Parliament
Vale Councillor Gwyn John Launches His First Novel at Llantwit Major Book Signing
Pink poppy display commences with celebration of life
Former Barry office block converted into new homes for people at risk of homelessness
Welsh Government publishes independent report on Level 4 intervention at Cardiff and Vale UHB
Three CoastSnap stations set to be installed along the Glamorgan Heritage Coast
Daffodil Runner statue installed at Marie Curie Hospice in Penarth
Woman Dies After Incident in Leckwith as Police Investigation Continues
Vale entrepreneur wins national Innovate UK award for sustainable construction technology