There is a green oak by the sea (У лукоморья дуб зелёный)
Well, to be serious. each of your options fits well, but I like "aquatic" much 
And BTW, I disagree that the word "Русь" is equivalent to "Russia". I am sure that the Pushkin's tale was about ancient Slavic state, called Kievan Rus'. http://en.m.wikipedia.org/wiki/Kievan_Rus%27. or just " Russ". The word "russia " comes from this word. So it is judicious to replace "Russia" with "Russ" (which IS NOT the same, whatever what modern russian propagandists want to say). However I fully agree with "russian" here.
December 31st, 2015
Alex, pls, not aquatic. It's good only for aquatic sports. And gentlemen, why don't you like "seafaring guardian", for instance? He's a tutor, though warchief sounds good for the old flavour of it. And Robin, thank you for that banging your head against the wall looking for the right word. Rings the bell so loudly. 
December 31st, 2015
Well, my English is not so good, so perhaps you are right. I just like the sound of the word "aquatic"
"Seafaring warchief" - that sounds PERFECT to me! Pathosly enough)))