**3. Conclusions**

The herein given overview of marine habitats, including their organisms, as a potential source of bioactive compounds, and especially enzyme inhibitors, shows that the field is highly dynamic and still growing in many directions. There are still plenty of putative inhibitors and their modes of action to be discovered. Here, novel methods and combinations of established routes will allow further compounds of interest to be uncovered. In particular, the high-throughput sequencing of genomes and metagenomes of even unculturable organisms will allow novel biosynthetic gene clusters to be discovered, which nowadays can be transferred by means of synthetic toolboxes of molecular biotechnology towards producing organisms. Thus, the production of so far silent or uncovered gene clusters will become more and more useful. Screening and robotics will further develop to assist all these efforts. In addition, we now have bioinformatic tools to pursue molecular dynamic studies, including compound docking, and thus targets and mode of action can be predicted with greater and greater accuracy. Therefore, it can be rationalized that we will see more and more of these products from marine environments.

**Funding:** D.T. was supported by the Federal Ministry for Innovation, Science and Research of North Rhine– Westphalia (PtJ-TRI/1411ng006)—ChemBioCat.

**Acknowledgments:** D.T. thanks the authors of the articles in this Special Issue for their contributions to the field. Further, the support from the MDPI editorial team is acknowledged.

**Conflicts of Interest:** The author declares no conflict of interest.
