The warning signs on a beach where a brother and sister got into difficulty in the sea before dying are "inadequate", a coroner said.
Malika Shamas, 14, and Haider Shamas, 18, died after being rescued from the water at Clacton, Essex, on 8 August.
The siblings, from Luton, died little more than a year after another teenager drowned while swimming nearby.
Tendring District Council said it would "consider how best to implement the recommendations made by the coroner".
The inquest in Chelmsford earlier this month heard the siblings, who could both swim, and their cousin got into difficulty near Clacton Pier at about 13:40 BST.
Malika died of immersion while her brother died two days later of pneumonia, brain damage and drowning.
The inquest heard there was a warning sign on a nearby flood defence which said "danger, no bathing due to varying depths of water" but coroner Caroline Beasley-Murray noted that you had to be quite close to read it.
In a prevention of future deaths report sent to the council she said she "had qualms about the effectiveness of existing signage".
The coroner said some of the information "was written in small text and hence difficult to read".
She also said more beach patrol surveillance would help "on such a busy stretch of beach" as the patrol officer was 395m (1,295ft) away and was "unable even with the use of binoculars to discern the nature of the incident".
She also referenced the 2018 death near the pier of 15-year-old Ben Quartermaine and added "warning notices by the pier might assist".
The council said its signage met national standards.
Mike Carran, the authority's head of sport and leisure, said it would work "to do everything possible to make our coastline as safe as it can be".
"This will range from reviewing our signage in line with national guidance, and continuing to promote education about water safety to our young people," he said.