Staff from Natural Resources Wales (NRW) are back in the sea, taking water samples from more than 100 of the country's beaches.
The summer testing season normally runs from mid-May to the end of September but was delayed this year due to the coronavirus pandemic.
It got up and running again last week at 105 beaches, from Barry all the way up to Prestatyn.
NRW said sampling will be less frequent than normal but will still be in line with the governing bathing water directive.
A NRW spokeswoman said: "We continue to monitor the ongoing advice from Government in relation to restrictions due to Covid-19 and may need to react to future guidance."
The water samples are brought to a laboratory at Swansea University's Singleton campus, where microbiologists test them for bacteria which reveal the presence of human or animal faeces.
Both of these can affect human health if swallowed, and can indicate run-off from livestock farms.
Annual ratings classify beaches as excellent, good, sufficient or poor, based on measurements taken over a four-year period.
The most recent classification for Aberavon beach and Swansea beach is good while Langland, Caswell, Port Eynon, Rhossili, and Carmarthenshire's Burry Port and Pendine are all rated as excellent.
Testing used to be carried at a laboratory on the outskirts of Llanelli before the new facility in Swansea opened in 2017.
