The manuscript is not ready for publication, for a number of reasons (many of which are shown in the attached file). The English language must be improved; the present version does not meet the minimum standard for an international publication, and in several points the language is not clear. Authors are invited to have the revised manuscript checked by a English native speaker. References are quite poor, and need to be integrated, especially as concerns the use of geophysical methods in karst coastal settings. I have suggested some references, starting from which the Authors could find additional work to cite.
When more references are listed, these must be arranged in chronological order.
Sinkholes are described poorly. Sinkholes in general, and the hazards related, should be worth of a specific paragraph, and the case study must be better described, also as regards their size and depth.
Many sentences are too vague, without data. For instance, there is a continuous reference to thin or thick roof, putting this in relation to the possibility of collapse. No number is provided. What Authors mean by thin or thick? Further, also as concerns the surveys by scuba divers there is no morphometric data to let the reader understand the size of the flooded galleries.
All the above issues must be clarified and integrated in the revised version of the manuscript.

Based upon the redviewers'comments, the article still needs adjustments before being considered for acceptance and publication

Even though the paper has improved throughout the revised versions, it still does not completely respond to the referees' observations. In particular, I totally agree with the request by the referee to include a Discussion section. Authors are kindly invited to revise their manuscript, trying to fulfill all the referees' request

Dear Authors, the discussion section you included, following our suggestions from the previous reviews, can be considered a starting point but in its present version it is still not sufficient (especially because it is written in a colloquial style rather than as a scientific contribution). I will try to better explain what we were talking about when asking for a Discussion section.
The Discussion should be intended to allow other researchers to apply the proposed method in other geological and hydrogeological settings. This means that you should in some way summarize the advantages and drawbacks of the applied methodologies, in the attempt to highlight whether it might be used also in other situations. I understand that the amount of data required by the reviewers would take a very long time, but an effort in providing further data from the literature or from similar approaches in nearby areas, aimed at making the article more appealing to other researchers, should be carried out.
With the addition of a more full and well-written discussion section, the article might be considered for publication. Hoping what is written above will clarify the matter to you, I am looking forward to receiving the new version of the manuscript

The manuscript is about ready for acceptance, after the last effort dealing with the discussion. There were however some errors in typing and few other things that obliged to ask for minor revisions. Please see what indicated in the attached file, and return the manuscript.