The cache is indeed bright silver, but it may be tricky. Respect the mighty Mississippi, it is a fast moving river. Landing this island is best done to the South, you will find a nice inlet with calm water to land on. BYOP.
Please note - this cache is in a potentially dangerous location and seeking it is done at your own risk! I strongly recommend against doing this in the winter, as ice on rivers is always unpredictable. Legal entry points (PWAs) are provided, other entry points may be considered trespassing on private property. The terrain rating reflects the need to travel a significant distance on water.