Overall this manuscript provides a short summarising view of groundwater as a linking element between land and sea. Its scope is adequate for the publication format and the argumentation is well made in several key points. The topic and scope are very timely and match a research area reaching a cumulative point of becoming useful in management contexts.  Albeit of considerable utility to the target readers, the manuscript reads mostly as a summarising text, where the authors' own contributions appear very scattered and hard to find; summarising their original contributions at the end of the sections might be a simple solution to enhance the manuscript's uptake and impact. I made several annotations in the attached pdf to be considered by the authors. Most reflect a need to alter the document to become more reader-friendly and add some contribution ambition, which is somewhat limited in this version. The point made about the common language/proposed framework for existing methodologies would be a particularly desirable adding value.

This article provides a summary of the important roles, ideas, and prospects of groundwater as an important link between land and sea. In particular, the authors classify meteoric groundwater into coastal runoff FSGD and offshore freshened OFG, and emphasize the role of each and the connectivity between the two. This manuscript is very timely and necessary as the definitions scattered in several papers were arranged, the latest research from around the world were cited, as well as a perspective or direction for groundwater study is provided. Nevertheless, some suggestions are annotated in the attached pdf to help the reader understand.