Illustrative route line through real stops, not to scale. Picton, the Marlborough wine trail, and Blenheim.
Picton is where most South Island self-drive trips physically begin, because it's the ferry terminal, and that accident of geography puts you thirty minutes from New Zealand's largest wine region and right at the entrance to Queen Charlotte Sound in the same afternoon. The trouble is that neither of those two things works the way the ferry-day rush usually assumes. The Sound itself has almost no road access, so seeing it properly means getting on the water, not just glancing at it from the highway. This page covers the logistics for a Marlborough trip built around both: how the ferry, the Sound and the wine trail actually fit into three to five days. For the cellar-door-by-cellar-door detail, see the Marlborough Wine Train Mixtape, which covers the wine trail properly and isn't repeated here.
Picton is the terminal, not the destination
Picton sits at the head of Queen Charlotte Sound, and the Sound is the reason to stay more than one night before heading inland to the wine trail. The Queen Charlotte Track, according to DOC, runs 73.5km from Meretoto/Ship Cove through to Anakiwa, and most of that distance has no road access at all: DOC's own notes list access to trailheads like Meretoto/Ship Cove, Resolution Bay, Endeavour Inlet and Camp Bay as being by boat only. That means the honest way to experience the Sound, rather than just its edges, is a water taxi, a scenic cruise, or walking or biking a section of the track itself. A half-day cruise out to historic Ship Cove and Motuara Island, of the kind Beachcomber Cruises runs out of Picton, covers the water access side without committing to a multi-day walk, and is the realistic option for anyone with three to five days rather than a week to spare on the Sound alone.
Skip driving Queen Charlotte Drive expecting to see the Sound itself
Queen Charlotte Drive, the sealed road linking Picton to Havelock, is a genuinely scenic 33km stretch with viewpoints like Cullen's Point looking out over the water, and it's a fine way to get between the two towns. Where it falls short is as a substitute for actually seeing Queen Charlotte Sound: the road runs along a ridge above the water for a fraction of its length, and the coves, bays and forest sections that make the Sound worth visiting sit well below and beyond what the road shows you. Treating a drive along Queen Charlotte Drive as "having seen the Sounds" is the trap: it's a good drive between two points, not a substitute for a boat trip or a walked section of track. The same logic applies to cramming a Sounds cruise and a full wine-trail day into the same day straight off the ferry. Both are worth doing properly, and both lose something if they're rushed back to back on arrival day.
The wine trail is thirty minutes away, and Renwick beats Blenheim as a base
From Picton, Marlborough's wine region is a short run down SH1 and SH6, and Renwick, not Blenheim, is the better base once you're there: it sits inside a 5km radius of around 15 cellar doors built largely around Sauvignon Blanc. Tasting fees vary a lot by winery, from free tastings at some smaller producers to $30 to $45 at a name like Cloudy Bay, so it's worth checking a cellar door's own site before assuming a flat rate across the region. This page keeps the wine-trail detail brief on purpose: the Marlborough Wine Train Mixtape covers individual cellar doors and how to string a tasting day together, and repeating that here would just be padding.
Give the Sounds a genuine half-day on the water via a cruise or a section of the track, and give the wine trail a separate day: stacking both into the same afternoon straight off an early ferry crossing means neither gets done properly.
The bit nobody publishes: the Cook Strait ferry doesn't land in time for the first cruise into the Sound. Interislander's own timetable shows the earliest Wellington departure around 8:45am, and a 3.5-hour crossing puts that sailing into Picton around lunchtime at the earliest, while Beachcomber's own Ship Cove cruise leaves at 8am or 9am depending on season. Travelling over on the day and expecting to collect a rental car, catch a Sounds cruise, and still make Renwick for an afternoon of tastings is optimistic, not realistic. Plan the cruise for the morning after you arrive instead of the ferry day itself, and the wine trail becomes a straightforward day after that, rather than a scramble.
This route is worth building a Marlborough trip around if you want a genuine half-day on the water in Queen Charlotte Sound as well as a proper wine-trail day, and if you're willing to give the ferry-arrival day itself a lighter schedule rather than packing it full. It's not worth it if all you actually want is the wine: in that case, skip the cruise and go straight to Renwick, and let the Marlborough Wine Train Mixtape do the planning from there instead of forcing a boat trip into an itinerary that doesn't need one.
Do I need a boat to see Queen Charlotte Sound properly, or can I drive it?
Most of the Sound has no road at all. A water taxi, a scenic cruise, or walking or biking a section of the 73.5km Queen Charlotte Track is the only way to see the Sound itself rather than glimpsing its outer edges from Picton or from Queen Charlotte Drive between Picton and Havelock.
Blenheim or Renwick as a wine-trail base?
Renwick. It's smaller and quieter than Blenheim, and it sits inside a 5km radius of around 15 cellar doors, so you're closer to the wineries themselves. Blenheim still makes sense as a stop for the bigger supermarkets, fuel and a wider choice of accommodation if Renwick's options are booked out.