Water Safety New Zealand is urging people planning to take to the water to remember the message 'If in doubt, don't go out'.
Several people drowned over the weekend, including a father and son who'd been snorkelling for pāua near Castlepoint on the Wairarapa coast.
They were Darren Southon, 48, and Joshua Southon, 11, both of Masterton.
The alarm was initially raised about the pair when they failed to return on Friday. Their bodies were found on Saturday evening.
Another person drowned in the water at Seatoun in Wellington on Saturday night and a kayaker is currently missing on Lake Ellesmere south of Christchurch.
Crews began searching for the man around midday yesterday and have since located his kayak, but he is still missing.
Water Safety chief executive Jonty Mills says people need to be prepared before going out on the water, and know their limits.
"Check conditions for whatever the activity you're undertaking and if in doubt don't go out.
"Diving is a really popular recreation that's growing in numbers and also that strong cultural affiliation through kaimoana, for food gathering, but unfortunately we've had three diving deaths so far this year."