"I couldn't be happier," Clark said. "It really is a great feeling. Only those that know me well can actually appreciate just how long and how much I wanted this. It's quite overwhelming to finally tick that box and finally call myself a Coast to Coast champion."
With past master Currie not racing as he focuses on qualifying for this year's Rio Olympics in triathlon, Clark was the race favourite - something he embraced in the lead-up, making it clear he planned on seizing the lead and being the man to beat.
Hunt, racing in his first Coast to Coast, held on for third, four minutes behind McLachlan.
Nelson's Elina Ussher won her third women's longest day title in 13h 32m after catching Myriam Guillot-Boisset (France) in the second half of the race.
Ussher overcame severe leg cramps during the run.
"It wasn't a very easy day for me but I'm very happy to win," Ussher said. "I really felt quite bad after the run but I knew I just had to race my own race and keep it going."
Guillot-Boisset held a four-and-a-half-minute lead after the mountain run but Ussher caught her an hour into the kayak to win by six minutes.
Hayden Wilde, 18, made it a Whakatane double, holding on to his overnight lead in the two-day men's individual event to win in 12h 18m, ahead of Gerard Morrison and Peter Olds.
Anna Barrett from Mt Maunganui also retained her overnight lead from the first day in the women's two-day individual event to hold off Isla Smith and Natalie Jakobs, winning in 13h 45m.