The warning comes as many are expected to head to the coast for beach holidays and days out in the UK across the remaining summer months.
A spokesman said: “In the past ten days, Her Majesty’s Coastguard recorded that nine people have sadly died while visiting the beach or coast.
“Each death represents a widescale tragedy for the families and friends of those who have died.
“Others have faced life-changing injuries.”
HM Coastguard is pleading with everyone to look after themselves, stay safe and avoid the dangers while at the seaside or coast.
Director of HM Coastguard 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.”
This summer the Coastguard reminds everyone to “Check tide times, remember the sea has currents, hidden depths and rip currents that can’t easily be seen.
It is 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 ever they need to.