Ever went on a small cruise around Jeju Island in Korea?

I do understand there is a marine park near Masan and Pusan. Is Jeju Island really like Hawaii?
Neither Masan nor Pusan are near Jeju.

There are ferry excursion boats from the southern port of Seogwipo but they don't go all the way around the island, and I never took one. There is car ferry service here from Pusan, Incheon (both 12-hour trips), or the southern part of the Korean peninsula (3 to 5 hours). Air service is less than an hour from every airport in Korea (about a dozen), and there are some 60 flights per day from Seoul.

Jeju isn't like Hawaii -- the climate is colder but warmer than anywhere else in Korea as it's furthest south. Many palm trees have been transplanted here from the tropics and they do well, so from the Korean perspective it look a bit like Hawaii. It's green year-round and snow in the littoral parts where most people live is rare. Jeju is the premier tourist destination in Korea; some five million visitors come here from the peninsula every year. Chinese visitors have been increasing dramatically year by year to this emerging tourist destination.

There are some marinas around Jeju, but the tradition of recreational boating isn't big in Korea and not so many people sail. Businesses provide pleasure craft service for a price, but that's the most of it.

The seas around Jeju are not green-brown; they are what people call tri-color blue. Since the white sand beaches are among dark lava rocks you get a patterned turquoise-aqua color (depending on sun conditions) where the sand is below, then a cobalt blue where the lava is under -- and of course as is the case everywhere the distant ocean is different, from blue to blue-green, depending on cloud cover etc. The only place the sea looks brownish is in the fishing ports or in the big port at Jeju City where the cargo ships come in -- and that's typical of harbor waters. Everywhere else around the island the seas are quite clean -- waste treatment is strictly controlled here and the population is less dense than most anywhere else in South Korea or Southern Japan.

As a tourist destination, Hawaii is far better developed than Jeju, still in its infancy from the perspective of international tourism (only a few hundred thousand foreigners a year but growing fast, by far most of them Chinese and Japanese). The airport landing strip isn't long enough to take the big jumbo jets so seats are limited. There are regular international flights, though, to four cities in Japan, three in China, and Bangkok. Jeju is at the center of the most populated region on earth, within an hour of Seoul or Shanghai or southern Japan, two hours from Beijing or Tokyo or Taipei, three from Hong Kong. A new long-strip airport is planned.

Jeju has an excellent road system (with signs in Chinese and English), so renting a car and driving around is very popular. At the middle of the island is a 2,000 meter extinct volcano (environmentally protected, covered with snow in the winter, and scalable by normal folk -- the tallest mountain in mountainous South Korea). There are some 360 secondary vocanic cones, some with perfect crater rims, lava tube caves some of which with calcium overdeposits, etc. The natural environment is strikingly beautiful, a major part of Jeju's attraction. Jeju has a fast-growing lesport industry but it cannot compare with what is available on Hawaii.

Archeology? some, but much more on the peninsula and in Japan.