Two teens were pulled from Tahunanui Beach in the early hours of Saturday.

Two skinny dipping teenagers were rescued by police at Tahunanui beach around 1am on Saturday morning.

The two young women and a young man stripped off and waded out on the sand bar near the Blind Channel at the western end of the beach, police said.

The tide turned and the young man was able to swim to shore, but the young women were stranded with a rising tide. The young man raised the alarm and search and rescue and the coast guard were paged to respond.

Sergeant Matt Elliott said two police officers were called out to the beach and had to strip down and swim out to save the pair.

The two officers had to take off their outer layers - "and all those things that we wear" - in order to swim out the 100 metres offshore to where the women were, he said.

An ambulance came to the beach as a precaution as the two had swallowed some sea water, but all three teenagers were "pretty good", Elliott said. The two young women were taken to hospital for observation and treatment.

He said it was important people practised water safety and common sense, and "chose the appropriate times to swim".

Search coordinator Senior Constable David Cogger said the western end of Tahunanui beach could be full of holes and deep water pockets and was not a safe place to go for a midnight swim.

"The Blind Channel in certain tides and wind conditions is a very dangerous place to be even in daylight."

Meanwhile overnight a group of four trampers had an unplanned and rough night in the bush after they strayed off the Boulder Lake Track near Takaka and became lost.

The group of four had five days' food and a locator beacon and were heading into the park on day one of their tramp when they got lost.

"It took quite some considerable time to actually work out where they were and it took two attempts to direct them back to the track," Cogger said.

"Department of Conservation and Landsar Golden Bay assisted Police SAR to direct the group back to the track."

He said modern technology was a great aid to those venturing into the outdoors, but a good current map and compass should still be essential parts of every gear list.

The group was finally directed back on track about 7.45 on Saturday morning.