Intriguing. Others more knowledgable will have more qualified suggestions, but:
I wondered if the gent with the cocked hat and full beard could be Prince Arthur, Duke of Connaught, son of our dear Queen, but I think he might be too old (The Duke was in his early thirties)- and it's hard to find an image of the Duke with a full beard although he does have that Saxe-Coburg look, still in evidence today.
He might be Lieut Gen Sir Edward Bruce Hamley, GOC 4th Division but I can't think why he'd be so prominent:http://www.npgprints.com/image/442038/m ... uce-hamley
The one with the hat a-thwart is probably the sailor of the crew- Admiral Seymour :http://www.npg.org.uk/collections/searc ... n-Alcester
The soldier with sun helmet and the moustache, and his arm over the side of the boat looks very like Maj Gen. General Graham V.C.: https://en.wikipedia.org/wiki/Gerald_Graham
Best I can do!