SIX great white sharks, some believed to be up to six metres - half the length of a bus - will be tagged by the Department of Primary Industries and the CSIRO this week.

Ballina mayor David Wright said the sharks had been spotted as close as 10m from the shore, in waist-deep gutters, and described it as a "scary" situation.

"They will try to capture the shark, turn it upside down, and put these tags into its tummy and then release the shark," he told ABC North Coast this morning.

"They'll be able to follow it for 10 years with satellites and things like that.

"They've never done anything like this before, these guys; they've done two-and-a-half metre ones and two-metre ones … but I think this will be a learning curve for everybody, but it needs to be done.

"We don't know if these are the same ones all the time, or if one lot goes and another lot comes.

"That's what they've really got to find out, and then they can work out what's causing the sharks to be right on the water's edge."