The Ōkārito River flows from the outlet of Lake Mapourika and travels roughly parallel to State Highway 6 for 4–5 km before turning onto the Forks Okarito Road corridor, passing the Wahapo Hydro Power Station, and eventually draining into Ōkārito Lagoon. The full run is rated Class II/III and covers enough distance to require either a car shuttle or a 17 km bike ride between put-in and take-out.

The standard put-in is at McDonalds Campsite on the shore of Lake Mapourika along SH6. Additional access points exist at several small lay-bys along the road, at the Trustpower Wahapo Hydro Power Station, at the Tidal Creek junction with Forks Okarito Road, and at the Okarito Historic Wharf. The upper section from Lake Mapourika is nearly flat Class I water. Gradient increases noticeably from the Forks Okarito Road junction, producing a series of Class II rapids down to the Power Station. The two most significant rapids sit immediately below the Power Station outflow, where the increased flow creates the trip's main technical challenges. Both rapids are described as easily portagable at sensible water levels. Below these, the river eases in gradient and meanders through wetland before feeding into Ōkārito Lagoon.

The final 4 km of the trip is a flat-water crossing of Ōkārito Lagoon to either the Okarito Wharf or Tidal Creek, where a lay-by and steps provide easy road access. The lagoon is tidal, and paddlers should be aware that tidal flows, afternoon sea breezes, and the slower pace of a packraft can make this section considerably slower than expected. Timing the lagoon crossing to avoid afternoon headwinds is advisable, and consulting local tide charts before departure is recommended. The DOC kayak trail brochure for the lagoon notes that paddlers should stay upstream of the wharf building, as the flow and shifting mouth of the lagoon beyond that point can be dangerous.

The surrounding environment includes some of New Zealand's intact temperate rainforest, with kahikatea and rimu standing along the water's edge. The lagoon itself, at 3,240 ha, is New Zealand's largest unmodified coastal wetland. The river also supports a resident brown trout population and sea-run chinook salmon, which enter from December through April. Estimated paddling time is approximately two hours from Lake Mapourika to the Wahapo Power Station, and a further two hours from the Power Station to Okarito.