A new survey shows an overall increase of 11% in dog mess on UK beaches - it's gone up 71% in Scotland.
Dog poo is dangerous because it contains high levels of bacteria - if it gets into water it can be very bad for bathers' health.
Almost 4,500 volunteers took part in the survey by The Marine Conservation Society - across 335 UK beaches.
The society says that pet owners have been thinking ahead by carrying plastic bags to clear up dog mess - which is a good thing.
But it now wants to encourage them to take the bags off the beach and bin it in one of the many dog bins provided.
Even though levels of dog poo were up, there was some good news: overall litter levels were down this year.

Last week, Paul Kenny was granted bail and banned from attending games after admitting racially abusing Sinclair.
"It was disappointing," said Gers goalkeeper Foderingham, an ambassador for equality group Kick It Out.
"No-one wants to see that in football, especially at a club I represent."
Commenting on the incident, the 26-year-old Englishman said it was "difficult when one idiot comes and starts to behave like that".
"The club has dealt with it accordingly," he said.
"The Rangers fans have been fantastic. All season and since I joined the club, they have been superb.
"I haven't (spoken to Sinclair), I can understand that he is probably upset and frustrated, but hopefully he will be all right."
Meanwhile, Foderingham admitted the Rangers players are still getting used to new manager Pedro Caixinha's methods since he took over from Mark Warburton.
"It is a different style of play," he said. "He is an intensive, aggressive type of manager who wants his sides to play as such and it will take time for the boys to adjust.
"We are doing that at the moment and hopefully we can get a good pre-season under our belts and have a good go at it next season.
"Until we start winning football matches on a regular basis, the question marks are not going to go away.
"So what we need to do is work together as a squad, as a management, as a club and get back to winning football matches."

Retailers must now ensure the products are covered up and no longer in public view unless a customer asks for them.
Shop managers and assistants who break the law could face fines of up to Â£5,000 and six months in prison.
The move follows similar restrictions introduced for larger stores and supermarkets in 2012.
Other outlets such as pubs and clubs also have to keep cigarettes out of sight.
Cardiff retailer Bobby Singh called the ban "pathetic" and said he did not believe it would stop people smoking.
Public Health Wales backed the new law and said the restrictions were a "very important development in improving health in Wales".
A spokesman added: "They will play an important role in reducing the appeal of smoking."
Pet owners who bag up dog poo and leave it on beaches are threatening the safety of people who visit the seaside.
[NEXT_CONCEPT]
Wes Foderingham acknowledged the hurt "one idiot" caused Scott Sinclair but says the fan, who admitted making racial gestures at the Celtic player, did not represent the Rangers support.
[NEXT_CONCEPT]
Display restrictions on cigarettes and tobacco products sold by small traders in Wales have come into force.