A large great white shark has been sighted in a lake on the NSW Central Coast, prompting warnings for people to take caution in surrounding waterways.

A commercial fisherman snagged the beast on Wednesday morning while casting nets off Canton Beach, on the north side of Tuggerah Lake, which opens into the Pacific Ocean at The Entrance.

A police statement said the man was forced to release his nets when the full-grown white shark, estimated to be up to seven metres long, became entangled in them.

NSW Police are working with Wyong Council, Surf Life Saving Australia, coastal patrols and the NSW Fisheries Department to monitor the area.

Police said people should take caution when using the interconnected waterways of Tuggerah Lake, Budgewoi Lake, Lake Munmorah and the Entrance Channel.

No one was injured during Wednesday's incident.

Inte bara bullsharks i wakeboardzonen...

SEVEN METRES..JEEEESUS H CHRIST...it's been a looong time since anyone has sighted a shark that big..I've been clse up with a 5m white and that was scary..jeesus 7 metres..that is one powerful eating machine..they eat dolphins and people WHOLE..

No they don't
But yea,that's one big fish.

Shit, i grew up next to tuggerah lake, don't think the shark would last that long though, even my mum wouldn't let me swim in the lake because it was so polluted .