The last year or so I feel like the random encounters of Megalodon and Skelly Ships have decreased a lot. I do not know if I am the only one who feels this, but as of latley I can play for hourse without encountering any of them while sailing. I miss those encounters. The open sea between islands feels a lot more emptier. I remember the times I was about to get to grade 5 before selling, and then a megalodon comes along just in time to kill it so I can reach grade 5. Or the panic you get when a skelly ship spawns in when you're loaded with chickens.
I am also have the same feelings about barrels of plenty. For some reason they also feels less frequent than before. Everytime I saild past barrels of plenty I used to jump the ship just to get some fresh supplies. And that kept me engaged when sailing between stuff.
I think the issue started when they expanded the map. This is just a guess, but when they expaned the map, they did not limited the spawn area for skelly ships and megalodons, and other stuff. I often can see skelly ships and The Reaper Chest way left, top or south of the map. I am not going to sail all the way down to F23 for a reaper chest, becuase, that is out in no where land. I no longer go for that chest because so often it spawns outside the general playing area. I wish they could add a restrictions that things do not spawn so far out (excapt for berrals of plenty and sunken ships (but not reaper chest) just so there are some incentive to be so far out).