A search for two missing paua snorkellers at Mataikona, near Wairarapa, is due to start back up shortly.
Police failed to find the pair on Friday after they were reported missing before midday.
Initial search efforts included helicopters, a surf life saving club and private vessels participating in a fishing competition.
Attempts later in the evening were scaled back - but still failed to turn up results before dark.
The missing pair are father and son.
"The Westpac Rescue Helicopter will resume a shoreline search followed by a search of the neighbouring ocean," police said on Saturday.
Their dive squad will also be out, followed by a helicopter sweep, if required.
"We have grave concerns for the pair's safety and we are working as hard as we can to find them," police said in a statement.
After the holiday period, Water Safety New Zealand chief executive Jonty Mills issued a warning to beachgoers, saying oceans and rivers needed to be treated with respect.
Mills urged beachgoers to swim between the flags where possible, watch out for rips and to wear lifejackets while fishing from rocks or while on a boat.