Waterfront property owners in north and central Queensland are being urged to prepare ahead of king tides, expected to swell up to six metres.
Townsville is expected to reach its highest tide of 4.11 metres on Wednesday, with Cairns to reach 3.47 metres.
In Mackay, the tidal difference between low and high water is predicted to hit more than six metres on Thursday.
People residing in waterfront properties are urged to move tinnies, kayaks and garden furniture away from the water's edge and keep a close eye on children playing in the shallows.
Maritime Safety Queensland general manager Patrick Quirk says novice mariners and visitors should take precautions to avoid being caught out by wider tidal margins predicted along the coast from Wednesday.
"This is especially the case in our more northerly ports where tidal ranges can be quite significant," he said.
"There is the possibility of low-lying roads and footpaths going under, especially if the tides coincide with high rainfall or storms as are currently being experienced in the far north of the state."