Because Connell does not explicitly describe Sanger Rainsford, readers must construct their own ideas about how he looks.  He is obviously a wealthy man who is able to travel the world on hunting expeditions.  He is a New Yorker. He carries himself confidently, and aboard the yacht, he tells Whitney, "The world is made up of two classes—the hunters and the huntees." He knows how to relax and enjoy a good pipe, which is what he is doing just before he falls overboard.

When Rainsford hears the shots from Ship Trap Island, "he leaped upon the rail and balanced himself there" on the yacht; this tells us that he is athletic and agile. When he swims to the island, he does so with "strong strokes," and when he awakens on the beach, "he looked about him, almost cheerfully." He is intelligent, blessed with keen eyesight, and is mentally and physically strong.

When he meets Ivan, he offers "a smile which he hoped was disarming." This tells us that Rainsford possesses social intelligence and knows how to manipulate people.

There is another clue about Rainsford's physical look; Zaroff is described as a "slender man," and when he gives Rainsford his bespoke suit, it apparently fits him.  Readers can extrapolate that Zaroff and Rainsford are not only a match intellectually (though certainly not morally), they are a physical match, as well. However, in terms of facial features, namely, eye, skin, and hair color, Connell offers no clues.

Connell gives us great physical descriptions of both Ivan and of General Zaroff, but he leaves Rainsford's physical description, pretty much up to the imagination. We can imply a great deal from Connell has given us, but there is nothing that says for certain what he looks like. We know that Rainsford must have tanned skin because he has spent the better part of his life outdoors hunting game. He probably has a rugged weathered look about him. He has good eyes because we know his aim is good or he wouldn't be a world renowned hunter, but we don't know the color. We know he must be physically strong and somewhat muscular or at least has muscular tone to his body because he swims a great distance to Ship Trap Island and he is not averse to surviving in the wilderness. He walks and runs a great deal while he is being hunted as well so it would take someone physically strong to do that for a sustained amount of time. He has a disarming smile that he uses when he first meets Ivan and General Zaroff. Other than that we don't really know much at all.