I see. Well, things don't have to have "clearly defined steps", I just gave a guide. If those things more or less already happen on a continuous level, then it's like @Gurken Khan said and "there's everything in the game already", or mostly. It's just that it's not intuitive, and until which depth land units (or from which depth water units) can transverse water should be stated somewhere, or maybe the cursor could change when a destination is not allowed because of this, or whatever similar. Only choppier waters (oceanic, or during storms even) would seem missing from what I mentioned, which is not a big deal but a possibility.

@Perzival12, did you make a new version of the mod maker? How is all that going?

I just changed the maps to get more area where ships and land units can interact.

Well, I updated my local branch with the remote branch and thats when i got this error.

Still some time remaining for my Athenian post, but in the meantime I'd advise against using the trident as a shield device, since that's very strongly associated with the Mantineans (actually, one of the best attested cases of an uniform shield device used by a city-state). On the other hand, "A" or "AΘΗ" have been found in representations, possibly used by some Athenians. If some "marine" symbology is wanted, an (ancient) anchor could be used, considering this particular case told by Herodotus: To this deme belonged Sophanes, who showed himself the best of all the Athenians in this battle; and of him there are two different stories told: one that he carried an anchor of iron bound by chains of bronze to the belt of his corslet; and this he threw whensoever he came up with the enemy, in order, they say, that the enemy when they came forth out of their ranks might not be able to move him from his place; and when a flight of his opponents took place, his plan was to take up the anchor first and then pursue after them. This story is reported thus; but the other of the stories, disputing the truth of that which has been told above, is reported as follows, namely that upon his shield, which was ever moving about and never remaining still, he bore an anchor as a device, and not one of iron bound to his corslet.