Anytime you arrive a new island, make a portal immediately. You don't have to build a base or anything crazy right away. Just bench>portal, that's it. You can then travel over to the boss and build out your base, moving your shore portal over a little later when things are safe. I know that's Monday morning QB'ing considering the position you're currently in, but it's good practice. It might be time to call in a friend to help you out.