# Underwater Drone Architecture for Marine Digital Twin: Lessons Learned from SUSHI DROP Project +
## 4 Conclusions  
As part of the Interreg project SUSHI DROP, a working prototype of a multi-purpose UUV has been developed and equipped with a multitude of selected instruments to non-invasively investigate the marine environment and produce population estimates of fish stocks. On-board sensors enable the acquisition of high-resolution optical and acoustic data while simultaneously monitoring physical, chemical and biological characteristics with precision. The prototype, called Blucy, is built with the possibility to operate in hybrid mode ROV or AUV. Among the various challenges for the realization of DT and accurate surveys of the seabed, until now largely unmapped, emerges the need for appropriate use of positioning techniques of the UUV and its sensors. Only through an accurate underwater positioning and a correct parameterization of the acquired information it will be possible to produce correctly georeferenced results and therefore comparable with other acquired data or subsequently replicable over time. Lessons learned as part of the SUSHI DROP project will contribute to the future deployment of a larger fleet of UUVs that will provide the scalability necessary to address the observation of critical habitats throughout the Adriatic Basin moving the first steps for the realization of a complete marine DT. In the near future, thanks to continuous technological innovations and scientific research, UUVs could achieve the same high level of efficiency, reliability and service economy that belongs to UAVs today.  
Conceptualization, L.D.M., L.V. and E.M.; methodology, A.L., M.M., J.C., A.O., G.B., M.B., E.M., L.V., P.C., M.C. and L.D.M.; software, G.B., M.B., M.M. and A.L.; validation, A.L., M.M. and J.C.; formal analysis, A.L., M.M., J.C. and E.M.; investigation, A.L., M.M., J.C., E.M., L.V. and L.D.M.; resources, A.O., G.B., M.B. and M.C.; data curation, A.L. and M.M.; writing--original draft preparation, A.L., M.M. and J.C.; writing--review and editing, L.D.M., L.V. and E.M.; visualization, A.L., M.M and E.M.; supervision, L.D.M., P.C., L.V. and M.C.; project administration, L.D.M.; funding acquisition, L.D.M. All authors have read and agreed to the published version of the manuscript.  
Figure 15: PilotCAM image sequence for mussel farming nets: Mitylus galloprovincalis.  
**Funding:** This research was funded by the European Regional Development Fund (ERDF), Interreg V-A, Italy-Croatia Cross-Border Cooperation Programme, within the SUSHI DROP (SUstainable fiSHeries wlth DROnes data Processing) project [[https://www.italy-croatia.eu/sushidrop](https://www.italy-croatia.eu/sushidrop)]([https://www.italy-croatia.eu/sushidrop](https://www.italy-croatia.eu/sushidrop)) (accessed on 15 January 2022) (Subsidy Contract n. 10046731).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors would like to thank [PERSON] and [PERSON], who had a special role in the design, construction and testing of the vehicle, FLAG Costa dei Trabocchi (Fisheries Local Action Group), IZOR (Institute of Oceanography and Fisheries) for the first missions at sea, SUNCE (Association for Nature, Environment and Sustainable Development), Split and Dalmatia County, and M.Sc. [PERSON] for all the support during the Italian surveys.  
**Conflicts of Interest:** The authors declare no conflict of interest.