On board the cruise, ambassadors will take part in organised discussion groups about the environment, social media and education as well as sharing their cultures and mingling in social activities.
"I look forward to being enriched by the entire experience while creating strong global connections," Ms Ratema said.
"Ultimately, I want to bring this all back to share with others [who can] be inspired to take up these types of opportunities for themselves."
Ms Ratema, of Te Arawa descent, said she looked forward to hearing different world views from people across the globe.
"It will be huge looking through the eyes and hearts of other people. And hearing their thoughts on different issues."
Ms Ratema will be holding a seminar on board the ship about youth involved in decision making, based on a Rotorua case study.
The former Rotorua Girls' High School student currently works at Waiariki Institute of Technology as a pathway adviser and has a history in youth work.
Placements are highly sought after for the trip and about 200 New Zealanders aged between 18 and 30 applied to be part of the team.
Ms Ratema thanked all her supporters including her whanau and iwi as well as those local organisations who sponsored her with gifts to give away to overseas ambassadors.
The Ship for World Youth will visit ports of call in Naha, Kobe and Ofunato before returning to Tokyo.
Participants from overseas were to start arriving on January 23, with activities in Japan running between January 24-27.
