At the time Mulcahy and fellow crewman signalman Frank Zalot Jr were among more than 15,000 US marines stationed on the Kāpiti coastline to train for upcoming battles.
On June 20, 1943, they were aboard one of more than 30 landing craft deployed from US naval ships anchored near Kapiti Island as part of a training exercise.
But it all went wrong. Their vessel suffered engine trouble. In a heavy storm, big swells and gale-force winds, it capsized after being hit by a big wave being towed back out to sea late at night.
The 25 sailors on board were dumped into the icy, turbulent sea.
Mulcahy and Zalot ended up in the water together. All around them they could hear men screaming “help, help, I can’t swim”.
Referred to as US Navy Chief Bosun's Mate, Mulcahy fought through massive waves in freezing surf, at just 4degC, to save Zalot’s life.
He saw Zalot struggling and sinking under the surface and yelled out “hang on Zalot, we’ll make the beach”.
Mulcahy managed to grab a lifejacket floating by and slipped his arm in one of the arm openings. Zalot did the same through the other.
But strong, outgoing tides dragged both men further away from the shoreline and out to sea.
All the while Mulcahy supported Zalot and kept him afloat in the frigid darkness.
“As Mulcahy and I drifted out we would sit on the crest of the wave for a couple of seconds and then quickly swoosh to the bottom of the swell up to the next crest. Those swells were 10 feet high,” the navy veteran Zalot said in his recount in 2012. “After about 30 minutes our lifejackets became waterlogged and we were no longer above water when the waves would crest. As waves broke over our heads, we had to use our free hand to cover our mouth and nose, trying to keep from swallowing or inhaling water. “We were too exhausted to hold our breath. It was still pitch dark and the roar of the wind and sea was very loud.” It was almost seven hours before a rescue boat finally located and pulled the pair from the water.
Tragically, 10 Marines died that day. Nine bodies were found on the beach the next morning. One man was never discovered.
Mulcahy was subsequently awarded the Presidential Unit Citation for his heroic actions and bravery. It is the highest unit-level award in the United States military.
“Mulcahy couldn’t swim at all, but he saved me from drowning,” Zalot recalled.
There’s a tribute to the sailors who drowned that day in the form of a steel landing boat that lists their names at the US Memorial site at QEII Park on the Kāpiti Coast.
Mulcahy died in 1973. Zalot died in 2017, aged 92.
Editor's note: This story was sparked by an inquiry from Grant Mulcahy’s great nephew Jerry Waite, who lives in Chicago, Illinois.