A:
Yes, you can swim at Marahau. Swimming is easiest when the tide's in, as there’s a large tidal range. If you want to swim when the tide is out, you may have to walk quite far from the beach. Swim at your own risk, as there are no lifeguards.

Gateway to the ever-popular Abel Tasman National Park at the top of New Zealand’s South Island, tiny Marahau is visited by most people on their way to the park. And that’s fair because the things to do in Marahau revolve around its location at the end of the road beside the national wonder. It’s where you might park your car before hiking, catch a water taxi, stay a night or two, or celebrate the end of a successful hike with pizza and beer at one of its small eateries.
You can visit Marahau at any time of year, but pick a fine day. The Abel Tasman National Park is extremely popular in summer (December–February), and many hikers pass through Marahau on their way into or out of the park. If you want to stay in Marahau at this time, book accommodation in advance. Thanks to its low altitude and generally sunny climate, you can hike in the park year-round or visit outside of summer to hang out at the beach.
Most people pass through Marahau on their way into the Abel Tasman National Park on foot or water taxi. Those transportation methods are preferred as you can’t drive a vehicle into the park, meaning if you drive, you'll leave your car parked and unattended in Marahau. However, there is no public bus service between Motueka or Kaiteriteri and Marahau. You can get a shuttle to the start and end points of the Abel Tasman Coast Track.
If you’re heading into the park on a hike, don’t wait until you get to Marahau to stock up on supplies because there’s nowhere to buy them. Marahau is a tiny village with a couple of cafés, some tour providers, and accommodation—and that’s it. Even nearby Kaiteriteri has limited options, with one small supermarket and some eateries. Stock up at sizable supermarkets in Motueka, Richmond, or Nelson before heading to Marahau.