Maritime folklore is both shared and separate from those living on land, so things can become complex. There is no question that sailors had their own beliefs and traditions. Those on land, living next to a maritime economy, often knew about some, but not necessarily all of the traditions. One could also argue that sailors perceived the stories differently since they were most likely to be the ones directly affected by the subjects of the stories, while those on land only consumed the stories as curiosities of a distant environment.

I have dealt directly with at least one of these sorts of traditions, namely those about the mermaid, and it may give us a clue about how to think about maritime folklore. (This appears in my recent book The Folklore of Cornwall, but the specific chapter is based on an article on Cornish mermaids that was changed slightly for the book.)

Many may regard the mermaid as something that is clearly an expression of maritime folklore. There is no question that she was a favorite topic of sailors, but stories about the mermaid typically describe her in the liminal tidal area between sea and shore. People on the land told just as many stories about mermaids at sea, and most of the stories describe encounters by land people rather than those aboard ships. So here there is a popular perception of mermaids being the property of sailors when in fact they are shared and in someways more celebrated by those on land. In the mix of this, there is likely to be a perception that this is the folklore of sailors, but it is more complex than that.

When it comes to sea monsters, there is likely to be something similar going on here (although I can't claim to have done extensive research on the subject). An analogy might be found in traditions about giants: pre-modern people believed in giants, but they relegated them to distant times or places. In other words, people would tell legends (stories told generally to be believed) about giants, but they would never tell a story about actually encountering one. Stories about giants might be used to explain an oddly placed boulder in a field (a giant threw it there long ago), or they might tell of stories about giants who lived in a distant place.

Similarly, people - particularly those living juxtaposed to a maritime world - were not about to pass up a story of a good, scary sea monster. This was something everyone wanted to hear about, and living near the sea, they were likely to be well-versed in a range of stories that the sailors told when they docked and spent time at the local pub! But the way sailors and people of the land interacted with these creatures of folklore was different: those on land would find the stories thrilling but remote; sailors would have heard the stories with more immediate fear striking at the heart. And more importantly, they might tell of encounters with strange things or of a terrifying night when monsters seemed to well up from the dark broth of a storm-tossed ocean!

Although not directly related to the question of monsters, with the disposition of the dead, one can glimpse something of the difference at the core of your question. Because the sailors were often lost at sea (or simply buried at sea), they did not enjoy the same status of land dead who were buried with ceremony and consecration in holy ground. This resulted in a certain amount of antagonism that seems even to date to a time before conversion. The following is an excerpt from my Introduction to Folklore:

There is at least one example of the successful incorporation of the idea of good and evil into the traditions of the peasantry. This occurs in the legend of the land dead and the sea dead. In this story, a young man walking along the coast at night insults the ghosts of the sea who begin to chase him. The frightened fellow flees through a churchyard and, hurrying past the graves, he cries out, “Up, up, every Christian soul, and save me!” He hears a tremendous noise behind him as he runs to his home. The following morning, the townspeople find jellyfish, sea tangle, and boards from coffins strewn about the churchyard. They conclude that the ghosts of the churchyard must have fought with the sea dead to protect the young man.

Christiansen classifies this story as Migratory Legend 4065, “Ghosts from the Land Fight Ghosts from the Sea.” The story serves as an example of peasants applying the Christian dichotomy between good and evil: the dead who are buried in consecrated church ground are helpful and good, while those who were lost at sea without burial rites are outside Christianity and are, therefore, evil. An early variant of the legend illustrates that this was not the original point of view.

The thirteenth-century Icelandic Eyrbyggia Saga includes an episode that is strongly reminiscent of Legend 4065. A series of illnesses left several people dead and buried, but their animated corpses began to haunt a certain farm. Shortly after this, a ship from the same farm was lost at sea and five sailors were never found. The household had a funeral feast for the lost men. No sooner were the people seated then the dead sailors entered the room, leaving seaweed and puddles of seawater wherever they went. The corpses warmed themselves by the fire. They returned each night, even after the funeral feasts had ended, but now even more dead people arrived, these covered with dirt, which they shook off and threw at the dead from the sea. The two groups, those buried on land and those lost at sea, met each night and quarreled until the owner of the household charged them with trespassing, at which the corpses left for good.

This early variant of Legend 4065 lacks a Christian point of view. Both groups of dead are equally troublesome, and neither has assumed a good or evil role although they are clearly antagonistic to one another, anticipating the later legend. Since recent variants of the legend exhibit the Christian dichotomy of the spiritual world, it seems likely that peasants modified Legend 4065 sometime after conversion. Although the legend is an example of the successful integration of the concept of good and evil, it is the exception and not the rule.

With all of this, we can see that whether sailor or those living on the shore, there was often a shared oral tradition, but they way the traditions were dealt with could be different depending on occupation.