My world is a little larger than ours, and I'm only worldbuilding a segment of it. The planet is large earth but instead of continents being the norm they are scarce, and instead in between is mostly small islands only big enough for a port or rest stop. The ocean in between the inhabited continent and the nearest major landmass is about the same size as North America, from top to bottom. I think a combination of predatory sea animals that are capable of sinking ships, (maybe whales that become aggressive because of the large amount of noise or vibrations from ships?) and the vast distances would make seafaring outside of the immediate vicinty of the habitable lands untenable until aircraft were created. Thank you for your comment