Incense spawns same Pokémon over and over when you are in the middle of nowhere

I live on a sailboat and I’ve noticed when I’m sailing in the middle of the ocean far from shore, nothing spawns. However when you use incense it overcomes the barren biome and spawns nicely. Usually it spawns a typical variety of Pokemon but quite frequently it bugs and just spawns the same thing over and over. My boat typically move about 6 mph, so it spawns pretty much constantly.

Here are logs from a sail I’m on now. If you have an appropriate mega evolution it can be a very efficient way to farm candy. Be better if it was meta-relevant, but you can’t have everything. It will spawn a random Pokemon in the middle once in a while, but not often.