The simple answer is that no, sailors were not "really more superstitious than the average person." To this I would add the caveat, "especially when it comes to those working in dangerous occupations."

That caveat aside, it has always been easier to recognize (and often to judge) "other people's" folklore, beliefs, and "superstitions" - a term that is often used in a judgmental way. Because sailors had their own brand of work-related folklore and yet they mixed with "normal people," maritime folklore often jumped out and became clearly visible to their non-sailing counterparts.

Much the same thing has occurred with mining folklore, traditions held by workers in an eerie, dangerous environment, not unlike the seas where the sailors worked. Again, because miners had their own distinct folklore, beliefs, and practices, often designed to harness supernatural elements for favor and/or to render harmless dangerous supernatural forces, non-mining counterparts often recognized (and judged) those traditions.

By contrast, we (whomever the "we" is), do not so easily recognize our own folklore because it is ingrained into our culture, and even when we may recognize certain beliefs and rituals, we are less likely to judge them - because they seem reasonable and familiar to us, as participants in our own culture.

Thus we might have a farmer who lives near a port and near mines; the farmer goes to great lengths at harvest to make certain that supernatural forces do not steal the "essence" of the last stalks of wheat, because in the process of harvesting, he has "chased" the life force of the harvest into the last corner of the field. To make certain this essence is saved and treated properly, the farmer may make a "corn doll," which he keeps above the hearth, all to make certain the forces of the world are kept in balance and he gets the "good of" his harvest. This seems reasonable to the farmer because he is doing something he was raised to do - and his parents did it before him. But the farmer goes down to the dock and encounters sailors who also have practices intended to balance the supernatural forces in their world; and then the farmer goes over to a mine where miners are doing the same. All the workers from these three occupations come from the same culture, but they have distinct occupational beliefs and rituals. The difference here is that the miners and sailors were, perhaps, raised by farmers (or at least around farms), so the farmer's practices don't seem strange, but the newly-adapted beliefs and practices of the sea and the mine, places that happen to be particularly dangerous and eerie seem very strange to the farmer. The farmer concludes, consequently, that the sailors and miners are "more superstitious than the average person."