Springtime is a beautiful season to visit Japan because of the blooming cherry blossoms. Though it is a peak time for tourists, you won't want to miss this natural spectacle. Some cruise lines even offer tours to the best flower festivals with stops in Akita, Aomori, and Toyama.
The months of March through May are actually Fall in Australia, which is the best time to visit the Great Barrier Reef. Swimming season begins in April with comfortable temperatures and less rain. Cruises that stop at Cairns, Port Douglas, and Airlie Beach allow for visits to the reef. You can also board a Great Barrier Reef-specific cruise to explore that area only.
There's no better time than in the Spring to visit the Dutch cities. Board a Holland river cruise to witness fully bloomed tulip fields, windmills, and historic cities. A number of river cruises start and end in Amsterdam with a couple stops in Belgium in-between and truly looks like the best way to experience the Netherlands this time of year.