"We need the dredge desperately," said Malcolm Druce, the unit's commander.

"It's got to the point where a lot of vessels that should not be struggling in the channel are struggling."

The dredging began last week, having been delayed by about a month.

NSW Maritime Acting Executive Director Hendrik Clasie said the delay was "due to unforeseen and tragic circumstances involving the dredging contractor".

"As a result, it was not possible to have the dredging completed by the October long weekend and start of boating season, as had been the plan," he said.

The dredge has been working near the entrance to Swan Bay. Around this part of the channel has been one of the worst areas for vessels becoming stuck on the sand.

Malcolm Druce said at low tide, the depth in that area was little more than a metre.

"This is the most shallow I've seen it for a while," Mr Druce said.

On average, during the past few weeks, Marine Rescue Lake Macquarie crews have been called out daily to tow a stranded vessel off the sand. Over the long weekend, the unit attended about six shoaling incidents, and a nearby marina helped out a couple of more boats. Both sailing vessels and cruisers have needed assistance.

"I'm astounded, I really didn't expect to see cruisers getting stuck on the sand," Mr Druce said.

Hendrik Clasie said during dredging, 10,000 cubic metres of sand would be removed from the sand shoal near the entrance to Swan Bay, "for stockpiling and possible later replenishment of other areas".

State Member for Swansea Yasmin Catley said it was "about time" the dredging began, and she renewed her call for a more permanent solution in the channel.

"The overdue and intermittent nature of the dredging work just goes to show we need a permanent plan for channel maintenance so that it's safely navigable year round," she said.

"It's a process that needs to be done on an ongoing basis," said Malcolm Druce.

"It's not only good for tourists coming and going, but also for locals."

Read more: Long weekend safety blitz on lake