I think I now understand why all these posts complaining about the wind direction in boats exist. Some people really don't know that dropping the sail and paddling at low speed will get you where you want to go. Keeping the sail up will just stop you dead in the water. In fact you're lucky the devs don't make you go backwards because a real boat would.

A tiny island full of spawns does sound difficult. My usual method of starting in the next biome over and stealthily sneaking in, slowly knocking down enemies on the way wouldn't work. Certainly never try this at night. It wasn't night when you were doing this, was it? That could explain why Prince was wandering around without a spawner nearby. Those guys can show up by themselves, but it's rare.

For future reference, the best weapon to keep leeches at bay is a hoe. It's also easier to run away when there's a clear path for doing so. Renovate like you own the place. But only in the daytime.