The warning comes ahead of World Drowning Prevention Day on Sunday and amid a surge in trips to beaches as record temperatures hit parts of the country.
According to Her Majesty’s Coastguard records, there have been nine fatalities at beaches in the last ten days, with others facing life-changing injuries.
Other media reports have hinted at a higher figure.
HMC said each death represents a widescale tragedy for the families and friends of those who have died and is urging people to look after themselves, stay safe and avoid the dangers while at the seaside or coast.
Director of HMC Claire Hughes said: “We can’t emphasise this enough – the sea has no respect for whether you’re local or not and whether you’re experienced or not.
“Please always check weather conditions and tide times before going out. The Coastguard will always respond to 999 and do all we can to get people home and safe.
“But be careful. Think twice about what you’re doing at the coast that might put you, your family and friends and even those who come to rescue you in danger. Watch out for each other and those you love. Get home safe.
“We’ve seen too many tragedies already this summer and we’re sad for those whose families have been left heartbroken by the loss.”
Tips on avoiding danger at the UK coast include checking tide times and to remember that the sea has currents, hidden depths and rip currents that can’t easily be seen.
HMC also said it’s best to leave inflatables at home and make sure you have fully charged phones or other means of contact.
The public is reminded to call 999 and ask for the Coastguard if they ever find themselves in difficulty in the water.
A 16-year-old boy has become the latest person to die after swimming in open water as England’s heatwave is set to be replaced by torrential thunderstorms.
A Cheshire Police spokeswoman said the teenager was reported missing at about 2.30pm on Thursday after swimming in the River Dee in Chester and, after extensive searches, a body was found shortly before 8pm.