Sarah Sjöström's coach Antonio Lutula and an event host acted quickly and removed the protesters from the pool.
The start of the 50-meter freestyle final was delayed a few minutes.
The organizer is considering reporting the incident to the police.
"We will discuss it with the competition management this evening," says Dennis Fredriksson.
He says it is difficult to protect against disturbances like the one on Saturday.
"We've had this competition for ten years and have never had anything like this happen. We'll have to evaluate this, but we don't want to have barricades or bars; we want people to be able to move around," says Fredriksson.
Sarah Sjöström, who came second in the comeback, on the incident:
It was different. I've never experienced that in a competition. These are real elves who do this.
What do you think?