Too many children are leaving primary school without being able to swim properly, say campaigners.
They say one in three get to year seven without being able to swim the length of a pool - about 25 metres.
The report by the Amateur Swimming Association (ASA) says all primary school children should have swimming lessons.
They say that nearly four out of ten kids have never been offered lessons at school.
Swimming is supposed to be compulsory at school for seven to 11-year-olds, the campaigners claim.
Swimming 'can save your life'
Children should be able to swim unaided for at least 25 metres - about the length of a regular pool, they say.
The government agrees - they say: "By the end of primary school, pupils must be taught to swim 25m unaided using recognised strokes on their front and back and use a range of personal survival skills."
But campaigners want more parents to take their children swimming, more local pools to be kept open, and more help for swimmers at secondary schools.
Olympic gold medallist Duncan Goodhew told Joe: "Swimming is a sport that's so good for you. It's one you can do for the whole of your life."
He said the key to solving the problem is to get schools to "be marked" on their swimming lessons.
The ASA's David Sparkes said: "Swimming is the only subject on the national curriculum that can save your life."
We asked you what you think about this and lots of you got in touch...
"It saves lives. When my little brother jumped in the pool without his armbands I jumped in after him and saved his life. See- it DOES save lives."
Tumi, Lancaster, England
"I want to be a Olympic swimmer... but our school doesn't teach us!"
Lilion, London, England
"I think children should learn to swim only if they want to or their parents want them to. Although it is a good skill to have, it isn't fair forcing students to learn how to swim."
Clazza, Belfast, Northern Ireland
"I agree AND disagree as some children don't want to swim because they get scared they'll drown and balancing on the water is quite hard. People can't force you to, it's not a 'must do' rule. BUT, otherwise it still could help you if you were downing."
Sharon, West Midlands, England
"At my school we have swimming lesson only in year 5 and 6. I did the 1 mile swimathon this year, I love it."
Amy, London, England
"My school goes swimming once a week every week. We had a swimming gala today and we came 2nd out of the nearby schools."
"I didn't get to have swimming lessons this time last year because our swimming pool was being replastered. This affected my swimming abilities. We were supposed to learn lifesaving skills. Now I can't swim in full clothing and save anything and I can't do any water activities that involve swimming in full clothing."
Gwyneth, Dorset, England
"It is important because if you fell in water you would have more chance of survival. I think children should be taught lifesaving skills, as I did, and it's really good to know you always have it there if you are in trouble."
"I think we should have a choice whether we take swimming lessons or not."
"I can swim but I hate going swimming with the school! I get pulled in every year to go but I hate it and would rather do maths. I also think children should only go if they can't swim or if they want to go."
Georgina, Essex, England
"I agree with this statement. Lots of schools don't organise for the children to have swimming lessons because of the costs. They should think more about the children's safety than how much it would cost."
Livvy, Surrey, England
"I think you should know how to swim because if you can't then if you go away to the sea and you can't swim you miss out a lot."
"Being able to swim is very important but I think they should also go to a swimming school, as schools cannot provide adequate lessons!"
Kayleigh-Anne, Essex, England
"I think all children should learn to swim as it's a life-saving skill. If someone ever falls in a lake or river what are they going to do if they can't swim?"
Tom, Essex, England
"I think it's important to be able to swim and they should be taught how to do it in primary school, but if people don't want to swim they shouldn't have to."
"All ages should be able to learn to swim, it is an important skill to learn in life. You need this skill to save your life if you are in any danger!"
Elsa, Nottinghamshire, England
"We learn to swim in KS2 - we have lessons in Year 3 and Year 4. We think it is important to swim to improve our healthiness as well as giving us survival skills. Water safety is very important to learn about. Some of us have just taken part in a swimming gala - we had great fun!"
Year 4 - St Francis, Swindon, England
"I disagree strongly because most of the people who don't know how to swim don't listen to what the teacher has to say. But some 10-year-olds can swim more than 25 metres. I know that for a fact because we are offered 10 weeks of swimming practice every year."
Owen, Reading, England
"Many children can't swim because they don't take advantage of what they have. People may start at a younger age, so when they get around to having school swimming lessons they would get the hang of it quite quickly."
Roxanne-Emily, Reading, England
"I strongly disagree with this report, saying that people are leaving primary school without knowing how to swim. Our school goes to swimming 10 times a year, in total 40 lessons. Plus most of my class can swim 25 metres. So, Duncan Goodhew, I think your opinion is wrong and most of my classmates think you're wrong as well."
Shamsul, Reading, England
"I think people should know how to swim because it could save your life and you could save people who don't know how to swim."
Rafia, Edinburgh, Scotland
"I think swimming is really important because it can save many lives! I've been swimming for two years and I find it really fun. I think every child should be taking lessons. It's a fabulous form of exercise and great fun!"
Cookie, Middlesbrough, England
"In our school we don't learn to swim! But we should."
Jonas, Sutton, England