Council regional compliance manager Patrick Lynch said: "This was a serious and completely avoidable incident. These convictions and fines pale against the tragedy that may have occurred.
"Quite simply, these people could have died and we need all boaties to learn from this," he said.
"Such incidents show how real the risk of a bar crossing is and we hope it's taken as a warning to be prepared and well equipped beforehand. Just as importantly, people should be prepared to change their plans and not attempt the crossing if unsafe to do so. The fish will be there another day."
The sentencing follows a growing list of tragic water incidents this summer, and a couple of "lucky escapes" in Waikato.
In the first incident on December 28, three people ended up in the water while crossing the Raglan bar, on the region's west coast. They were rescued by a jet skier in the area.
Less than a week later, on January 3, two people were thrown into the water at Tairua, on the Coromandel Peninsula's east coast. They were picked up by a surf life saving club IRB.
The following day, at Matarangi, again on the peninsula's east coast, three vessels came into difficulty after losing power coming back in over the bar. A regional council maritime vessel responded and coordinated the initial rescue, which involved the use of jet skis to recover the six people from the water. Maritime officers later towed another vessel back to harbour.
A fifth incident occurred the very next day when a boat overturned in the surf off Pauanui beach while attempting to assist two kayakers, resulting in a fatality.
Council regional harbourmaster Chris Bredenbeck said: "It's the riskiest activity you can carry out on the water and it's a real worry to have had these separate bar crossing incidents on both our coasts."
Bredenbeck said weather, current and tide conditions cause waves to break in an unpredictable pattern on bars, creating an unstable and hazardous environment.
Sand bars are common around the country in areas such as harbours and rivers. To get out into open seas you usually have to navigate them, and they can be extremely dangerous, even for experienced boaties.
Those planning to undertake a bar crossing should:
• Thoroughly check marine weather and pay close attention to the swells.
• Check the tides and avoid crossing a bar at low tide.
• Seek local knowledge before attempting to cross a bar.
• Secure loose gear and ensure everyone is wearing a securely fitted lifejacket.
• Always take two forms of waterproof communication so help can be sought if needed.
• Spend some time observing the bar before attempting to cross it.
• Contact Coastguard on VHF to let them know your intentions to cross the bar and that you have made it across safely.
