We are having volunteers collect survey data and therefore the survey will be open to the public. Do you know if only the survey can be made visible to the public, but not the feature layer? The survey is for dispersed campsites so if people could figure out how to view the feature layer it might end up doing more harm than good. I thought I had to have the same sharing for the survey and feature layer for it to work. Does anyone have experience with this?
The short answer is "no". The survey will need to be able to access the Feature Service to post edits to it, which means that the underlying data needs to be public as well.
Things to consider:
If your users do not need to see the data, consider making it so that editors can only see their own features, or even that they can't see any.
Also, public surveys usually make sense to only have the Add capability, in order to preserve the integrity of people's responses.
Layer views can be a very handy way of dealing with public layers like this. One possible solution is to create a hidden field in your layer called "valid", and have your survey automatically assign a value to this field. Then in a view of this layer, you can simply filter out all features that do not have the auto-assigned value.