The Mangamate, combined with the Mangakirikiri are the 'official' way into Mangakirikiri Hut on the Motu, though in low flows dropping down the Motu from Otipi Road would be easier ...
Whilst the Mangakirikiri has deep pools and gorges, the Mangamate is the challenging part, combining these with waterfalls, logjams and slot gorges sometimes no more than a meter wide. Swimming was essential.
See the associated article / GPX file / track for a route guide.
(and yes - you do have to swim that pool and climb that waterfall. There is no way round).