The application by Ngati Pahauwera aims at establishing the iwi title to coastal areas in an area north of Napier.
NPDT chairman Toro Waaka says establishing title to coastal areas that were "never sold" is important if the iwi is to "stop seabed mining, pollution, and the ongoing destruction of our coastal fisheries".
"Ngati Pahauwera is presenting a case that establishes our interests whilst recognising other iwi roopu within Ngati Kahungunu whanui have interests as well," he said in a Facebook post.
Opening statements were expected to take at least two days, but one witness scheduled to be called said he was prepared to sit out the whole hearing to be able to have his say.
At least 49 witnesses are expected to be heard, most called by Ngati Pahauwera counsel, who opened by highlighting the Mohaka-based iwi's presence by saying it had 85 hapu groupings that "still have strong identities".
Submissions to the separate Environment Court hearing at East Pier are being made on behalf of seven entities, including the regional council, national organisations the Royal Forest and Bird Protection Society and Whitewater New Zealand, river watchdog group Nga Kaitiaki o Te Awa a Ngaruroro, and three lands trusts.