I have a massive map that causes lag issues because some islands require more process-heavy scripting than the others. The map is basically a giant sea with islands in it. Is there a way I can only render in one island where the player is near or currently on while the others remain unrendered not affecting lag issues?
You could either seperate your map into different places, or use content streaming
https://create.roblox.com/docs/optimization/content-streaming