I would advise taking a pair of 10 X 50 binoculars and a pair of pocket 10 x 24 compact binoculars. The wider view of the 10 x 50 will help in viewing from the ship and they will also gather more light. However they are not compact. The 10 x 24 are a good compact binocular. A good Pentax or Bushnell binocular in both models can be purchased for $150 or less.
I personally use a 26X to 100X spotting scope on a tripod. This gives adequate stability in everything in all but heavy seas. I find it a wonderful addition for a cruise but I wouldn't advise someone bringing one unless you are really into ship or island watching from the ship. It's another example of what one person brings has no use for someone else.
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