Montague Island Discovery Tours skipper and diver Warren "Wazza" Stubbs said he had never seen whales active for so long, and they breached thousands of times.

Usually, the whales would feed for up to an hour at a time, but these were like "dynamite" from 8am to sunset.

There was lunge feeding, tail slaps and pectoral slaps - where a humpback slaps its huge pectoral fins while it sculls in the water.

"Everywhere you looked on the first trip, we saw a breach," Mr Stubbs said.

READ MORE:

On the second trip, the whales' behaviour changed and they united from far and wide to become "super pods" of 30-40 whales.

He said the "elephants of the sea" were feeding beneath the surface and did not move from that area all day.

Mr Stubbs, who is guiding his 12^th whale season, said the ocean was an ever-changing environment.

There were less than average numbers of whales in the Narooma area between September 10-20, he said.

Merimbula sightseers, however, reported more than 100 whales feeding in water near Haycock Point at this time.

Mr Stubbs believes the high numbers at Narooma on Sunday could be "banked-up traffic".

Plus, there was plenty to feed on.

Mr Stubbs said while humpback whales had a sense of self-awareness, vessels nearby should slow down to idle and give them a wide clearance.

Bermagui commercial fisherman Jason Moyce also called on boaters to slow.

"These pods are some of the biggest pods I've ever seen, and the fact they are feeding and swimming in all directions can make it hard to avoid (hitting them)," Mr Moyce said.

"We found ourselves surrounded a couple of times lately, and just pulled the boat out of gear and waited.

"A couple of boats have hit whales in recent years and speed is generally a big factor. Whales are powerful animals and shouldn't be taken for granted."