If you build your own island with piles of dirt or rock far enough from the shore, but not so far where you can't see the bottom of the water. Then you won't have to really worry about monster invasions. The game won't really know how to path the mobs properly, and if you do get an invasion most of the time they won't even make it to your island before the timer on the invasion runs out. They basically spend all the time during the invasion trying to swim to you. Also your base won't take damage if you're not there. So during an invasion you can just hop into a portal you built to some random shack you found. Hang out there until it gets an invasion, then go back to your base. The game won't do two invasions at once, and the second one will cancel out the first.