The general circulation currents around the Hawaiian islands have been described as running about a third to a half knot in speed. See:
Integrated Ocean Observing System
http://oos.soest.hawaii.edu/pacioos/outreach/oceanatlas/currents.php
More particularly in places like the Molokai Channel the currents are described as being faster and more treacherous. Search for information about “Molokai Channel” “currents” for examples of the discussions and descriptions from the people who swim, paddle, sail, and motorboat in those currents.
The survivors were picked up by the rescuers at distances of about half a mile to one mile from the crash site, which is very consistent with sea currents running at or greater than the 0.5 knots described as typical for the sea currents outside the restricted waters among the Hawaiian Islands.
For a general idea where the survivors were located in relation to the crash site and the airport of their departure, find the rescuer videos and note the relative position of the island in the background of the view.
Currents that slow sound like tide influened not current influenced.. For instance here at the apex(middle) of the Gulfstream we anticipate a 2-2 1/2 knot current which is rolling right along. Add which way the wind is blowing subtact drag and you can get an idea.Probably not 100% accurate but somewhere in the realm of accuracy.