Hi Taya, 

thanks a lot for your advice. I was not aware of the dedicated guidelines for this and like to follow up accordingly.

Regarding 

Step 1) Regarding the biggest concern of overlap I can tell, that this is minimal so far, as the seagrass tag is relatively new both in internatinal IHO code INT-1 and OSM seamarks.  The current example is at islands Ios and Iraklia in Kyklades and this one I have taken good care of to not overlap with the import. Further, the coastal waters lack seabed information and there is so far no risk of overlap with existing seagrass and seabed tags in the near shore coastal areas in Greece. Indeed the import of Seagrass Meadows in Greek Sea near shore, after becoming visible, will likely motivate others to use, apply and further amend these OSM tags. That is the intention of the import in the best sense of OSM mapping.  

Step 2+3.1) I will clarify CC BY 4.0 waiver with scientific authors 

Step 3.2 and following) 
I will apply and follow the Guidelines with an appropriate process. 
If I understand right, I need to open a dedicated wiki page.  I will use https://wiki.openstreetmap.org/wiki/Import/Plan_Outline. Much of the work for adjusting to OSM and validating tags, including a very good comparison between my earlier findings and the outcome of the scientific report, I have already completed, so quite clear to describe it. 

Where I could really need some advice is the size of imports. I have the entire set of data for Seagrass Meadows in Greek Sea as one OSM, validated, all errors solved. This is what I tried uploading and it looks, the size was ok, but here I'm not certain. Can you tell me, whether there is a need to artificially split this changeset or can it stay in this size.

Any further advice and comments are welcome.

Josail

