At least 155 Sharks have been spotted in South Australian waters this summer, an increase on last year.

"We have no idea at this moment why that is, but safe to say Sightings have increased by 13 per cent," Surf Life Saving SA lifesaving and emergency operations manager Daniel Willetts said.

Beaches between Somerton and Grange continue to be where sharks are most frequently spotted, with bronze whaler sharks the most common.

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But experts say the increase in Shark Sightings doesn't necessarily mean there are more of the animals in the water.

"Having sharks around metro regions or beaches is not unusual for this time of year," Associate Professor Charlie Huveneers, a marine biology expert from Flinders University, said.

"It might just be linked to environmental conditions that leads them to come to metro areas more this year or more next year."

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Surf Life Saving SA is urging people to remain calm despite the rise in sightings.

"Please listen to the lifesavers, assets, evacuate water and stay out of the water until you're given all clear."