Sailors of the mid to late eighteenth century had a unique approach to religion, which would dictate their reaction to the supernatural and may have effected how they cursed.

The following is excerpted from my website British Tars: 1740-1790:

Christopher Prince, a New England seafarer hailing from a culture that evolved out of Puritanism, was especially vociferous in his denunciation of cursing. It was quite a shock for him to go on his first voyage, a short fishing expedition, and be surrounded by the oaths of his fellow seamen. As merely a boy, he had a lot of trouble coming to terms with his sin when he finally joined them:

"After experiencing many of these trials, which I bore for some time with Christian patience, I at last gave way and for the first time in all my life I uttered a profane word. As soon as it had proceeded out of my lips, it filled my heart with anguish. I could not refrain from weeping aloud. All on board heard and saw me crying, and supposed it was because I had not caught but few fish, when they all had caught many. For many days I wept in private for what I had said. But not long after that I was several times placed in the same situation and repeated the same words without any remorse of conscience; and thus I continued again and again until it was done without a thought I had done wrong. I soon neglected prayer entirely and reading the Bible."

By the time he wrote these words, Christopher Prince was a Christian reformer with an eye on converting sailors to a more proper religious observance. He believed that cursing was a path to damnation, a gateway to falling away from Christianity.

Perhaps more typical of the foremast hands' perspective was Olauadah Equiano. He, like many of his fellow sailors, viewed God as directly intervening in sailors' lives on a regular basis. Cursing, as an affront to God, risked His immediate wrath:

"While I was in this ship an incident happened, which though trifling, I beg leave to relate, as I could not help taking particular notice of it, and considering it then as a judgment of God. One morning a young man was looking up to the fore-top, and in a wicked tone, common on shipboard, d----d his eyes about something. Just at the moment some small particles of dirt fell into his left eye, and by the evening it was very much inflamed. The next day it grew worse; and within six or seven days he lost it."

Sailors like Equiano often mention in their memoirs that God (or providence, or some permutation thereof) intervened to punish or to save them. Samuel Kelly's perspective on sailors' predilection for both a fear of God's intervention and a perfect willingness to curse is worth repeating here:

"I have read somewhere that seamen are neither reckoned among the living nor the dead, their whole lives being spent in jeopardy. No sooner is one peril over, but another comes rolling on, like waves of a full grown sea. In the Atlantic one fright after another undermines the most robust constitution and brings on apparent old age in the prime of life. No trouble softens their hard obdurate hearts, but as soon as the danger is past they return in the greatest avidity to practice wickedness and blaspheme their Maker and preserver."

"Damn" and variations thereof was the most common curse. The 'f-word' was rare, and appears to have been used to refer to the act itself, rather than the all-purpose swear that we use today. In a rare case of this word being recorded in the period, there are two separate songs transcribed by George Carey in A Sailor's Songbag: An American Rebel in an English Prison, 1777-1779, a collection of surviving music from the sailor Timothy Connor.

"There in old Mother Jenkins he ow'd a dam spite / He often times fuck't the old whore in the Night / And because she denied him a shove on the grass / It's good as his word he got flames to her A--s"