On Google Earth 31°33'32.01"N 25° 9'50.53"E you can see Sollum actual small harbour....
the town is a lot bigger than 1941 but the sea is the same.... as you can see to be very realistic i could draw the sandy bottom that appears to be in the east part of the gulf, the rest is enough dark.... i dont think it is wise to insert elements in the map that have not a scope..... the question in this case is that it should be a meaning for the different colour.... they could be of 2 different colour for G13.4 Shallow/Deep OCEAN hexes meaning, but i didnt preview any seaborne assault and there wasnt a landing there in all the WW2.... the sea isnot made of plain blue but there is a texture (not perfectly viewable at this resolution)
You will for the rules have to define the Ocean hexes and Beach Slope, as this might on some aspect of play matter (even if only in 1 : 50 playings...the Sand state also matters as a result of the Beach Slope)...or you have to say all Ocean hexes are unplayable...but them we still need to know about the Beach
Had the satellite imagine been taken on a different day...
Also if you look at LFTs ocean/hinterland board you will see wave action on the shore (a separate point to having color depth)...I believe recent MMP river boards show a touch of white toward the shore lines. All this is to say is that there is a reason to pat attention to such subtle features.
My point was you made all this beauty on land, and then just defaulted to X blue "blah" in the ocean. This takes away from your map, IMHO. But that is just my view.
In any case wish you well with your project and look forward to seeing it in print.