Over 10 years since I walked that way though - it was lovely starting at the caves and finishing at the beach.
I went the other way and there is a alternative route from Hanson Bay for the KI Wilderness walk ...it is signposted "to Hanson Bay road" and briefly visits the rd.
I went the other way, and knew to look for the boat that obviously had to be on the river and it was easy to see and only 50 metres down to it. So can do either way but crossing is not essential the usual route
Actually I didn't cross the river at all; the trail came out at the beach on the east side of the estuary. I'm rather envious of all the people who have been on KI lately!
I'm a bit envious of Yak's version!