Monster 10m swells have been pounding the Western Bay coastline - causing containers to fall from Rena and prompting officials to warn people to stay off the water.
Maritime New Zealand hoped the weather would be clear enough to send up a plane this morning to check the damage to Rena overnight.
Late yesterday afternoon waves of 10m were recorded at A Beacon in Tauranga's harbour.
Tauranga Coastguard operations manager Simon Barker today said most of the time the swells were about 8m but at times they were bigger.
Coastguard duty marine controller Garth Hewetson said waves that size could be disastrous for small boats and he advised extreme caution to boaties thinking about heading out on the water today and tomorrow.
"These conditions don't make for comfortable sailing and we express caution and advise people if they really want to go out, to stay in the Tauranga Harbour.
"Big boats might be able to make it but any little boat that puts its nose into big waves like this, it's going to be very dangerous for them.''
Waves crashed up on Main Mount Beach yesterday and almost reached the Mount Surf Club.
Club manager Shelley Kerr described the area outside the club as "Lake Maunganui''.
Two gear trailers had to be removed from the beach and taken into storage areas to prevent them being washed away.
"The waves are big out there. It's breaking out past the blowhole, there's no surfers out there, it's too big.''
It will be six months tomorrow since the Rena grounding and rough seas at the Astrolabe Reef caused more containers to fall off the wreck late yesterday and a small amount of oil has leaked from the ship.
Maritime New Zealand (MNZ) confirmed the lost Rena containers fell from a hold in the bow section.
MNZ Tauranga response and recovery manager David Billington said an observation flight yesterday afternoon had confirmed swells had forced a hatch cover off the number 3 hold in the bow section, and an estimated 10 containers had been released from the hold.
One container was seen floating near the wreck.
It is possible the others had sunk to the seabed, he said.
Salvage operations could not take place in rough weather but salvage and container recovery teams were monitoring the situation and had contingency plans in place.
Mr Billington advised any boaties on the water to take extra care and observe the two-nautical mile exclusion zone around the wreck site.
The threat of hitting containers from the Rena has led to TeamVodafone Sailing, the favourite, pulling out of this weekend's Auckland to Tauranga Yacht Race, NewstalkZB reported.
National on-scene commander Rob Service said a small amount of oil had escaped from the ship and it could reach the shoreline.
More bad weather expected in next few days.
Conditions on land were also expected to be hazardous today, with strong southeasterlies rising to gale-force with wind gusts rising to 110km/h.
MetService meteorologist Daniel Corbett said wind would be the biggest problem in the Western Bay today and tomorrow.
"It will be a bit stormy but the showers will start to fizzle later in the week so unfortunately it looks like a wet start to the [jazz] festival down there but is certainly looking to clear on Sunday and Monday.''
`He said about 20-50ml of rain was set to fall in the coming days and temperatures were expected to remain around 21C.