One Way In
While having a survival retreat is a good thing, it's important to remember that having only one way in means there is usually only one way out. Limiting your options may not be a very effective strategy for your survival. A survival retreat that is located in a remote area may be what you're looking for but it will still need to be accessible by more than one means or route.
If for some reason you need to get out for whatever reason and the only way in is blocked, you may find yourself in a very bad position with little or no control over the situation. Having additional ways to get in will help you avoid this type of predicament. It will also mean that you have more than one way to get out if necessary.
Never place self-imposed limits on yourself when your survival is at stake.
Staying above the water line!