Sharks in their natural habitat should not be a concern. They are natural predators and perhaps they are circling their prey. The bigger concern is humans invading their habitat.
Many species of sharks circle. Its nothing to be concerned about, generally they are circling because they have found prey. stay clear of them, you'll be fine!
Although columbian sharks are small compared to most sharks, any sharks swimming in a school should be approached with caution. As long as you keep your distance you'll be fine.
I would be concerned seeing any sharks in a group swimming in circles as this may indicate that they are feeding and circling their prey. I would avoid any water in which the sharks were circling.
