Now that you mention it, I remember someone pointed this to me once. You are right.

But Camoes significantly improved the original expression. He could have used the Portuguese word "necessario" which is exactly the same as "necesse" and "necessary".

Instead, he cleverly translated "necesse" as "preciso", meaning both "necessary" and "precise". This gave the expression a second meaning, and both of them are interesting reflexions on sailing and life:

The need to sail surpassing the need to live and the mathematic precision of navigation as opposed to life's uncertaintys.

Beyond philosophy, the second meaning praises the sailors whose stories he wrote about. The Portuguese and Spanish excelled in navigation and at that time they were the only Europeans who could say navigation is "precise".

Camoes expression is far more interesting and meaningfull than the original. I stick to him.

Cheers,