They also need to be able to take a ribbing and give as good as they get. Chirpy chappie Dickie was that.
Dickie got the job as a 17-year-old and guided a quartet of robust, firm-minded individuals, Dick Joyce, Dudley Storey, Ross Collinge and Warren Cole, to a surprise gold medal in Mexico City.
Three years later, he was calling the shots with an eight who won the European Championship title — effectively the world crown — and repeated it a year later on the Feldmoching course in Munich.
New Zealand were convincing winners, a magic occasion when the amateurs from far away toppled the East German professionals.
As Dickie once put it succinctly: "Subsequently of course, we've learnt that there was a significant amount of enhancement to their performance by way of what we would now commonly call cheating.
"You didn't actually need to be a professional, you didn't need to be a cheat — you could be just a wholesome bunch of guys."
Then, for the first time, God Defend New Zealand rang out as the New Zealanders stood on top of the dais.
"We were bawling like babies," crewman Wybo Veldman recalled recently. "Totally unexpected. Awesome."
Dickie, beaming at the end of the line, was 21 and had his second gold.
"It was an extraordinary combination of minds that were singularly aimed at achieving a common goal, which was to win," Dickie said of that crew. "It was an extraordinary dynamic of individuals."
And Dickie? What was the secret to his ability to draw out the very best?
"He was a larger than life personality, which was a prerequisite for an excellent cox," Munich gold medallist Athol Earl recalled this week. "He had a belief in himself, in those around him, and he had the confidence to drag you with him. You couldn't help but look up to him, even though we were six foot six and he was five foot something."
New Zealand have been blessed with quality coxswains but Earl was adamant: "None would come near Simon."