There are a number of islands that are actually steep rocks in the sea , and visiting them would require such daring feats of navigation and mountaineering that the trip is hardly worthwhile.
For example, in the early 2000s, a group of Australian entomologists climbed this island at night to find insects:
The insects in question, Dryococelus australis , also known as the "land lobster" or Lord Howe Island Stick Insect, had been thought to be extinct for nearly a century. As entomologists, they were excited to find live insects. As Australians, they thought it was a good idea to climb a rocky spit (known as Ball's Pyramid) in the middle of the sea at night. I'm all for the pursuit of science, but I can think of better ways to spend a holiday.
In any case, I suppose the questions don't really refer to places like this, because there are thousands of these inaccessible rock formations in the world's oceans, and very few of them would make beautiful places to visit.
I would rather submit an application among the habitable islands, where one could actually stop to take a look around or possibly relax on a beach or something.
This candidate is North Sentinel Island .
It appears to be a tropical sandbar in the Indian Ocean, which is perfectly uninteresting. The island's most troubling characteristic lies in its inhabitants, who are legally protected from all outside contact and are notorious for killing foreigners who dare to violate their territory. For example, they murdered a 26-year-old American missionary who had landed illegally to preach the Bible. Considering the fate of most other indigenous tribes after the Bible was preached to them, I can't say they were entirely wrong.