White tips but not Whitetip = Silvertip?

[isurus]

worth mentioning perhaps that in some areas (although certainly not in your case which sounds silvertippy as they come) there is antoher possible confusion species if you just look at the dorsal fin as there is a colour morph/subspecies of grey reef shark - Carcharhinus amblyrhynchos wheeleri (sometimes referred to as C. wheeleri the Shortnose blacktail shark) which can show a white marking on the dorsal.

 

[vladimir]

I think the easiest way to differentiate between these species, especially from above, is to note the blunter nose of the whitetip, and its slender body.

 

[rickydazla]

I disagree, I think noting which of the fins have light tips is the easiest way. Neither of these sharks has a dark band on its tail fin.