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<blockquote>It counters intuition that although a light fails to illumine the area between the source and the target, the light can still illumine SOLELY the target!</blockquote>

The light is illuminating everything.  The photons don't magically disintegrate some fixed distance from the light source.  The illumination gets smoothly dimmer with distance.  At some distance, the light is dim enough so that it <i>appears to your eyes</i> like there is no illumination.

Your question doesn't explain what these "markers" are, so I'll assume they are buoys put there specifically to be visible.  In that case, they most likely have areas with retro-reflective paint on them.  The point of retro-reflective paint is to reflect light in about the same direction it came from.  That means a high percentage of the light from your lamp that hits these markers is bounced back into your eyes.  This is certainly not true of the water, which will reflect most light away from you.

The markers are reflecting many times more of the light that hits them from your lamp than the water does.  As a result, they look brighter to your eyes than the water does.