Marsters said it was a dream of his to play at the Rugby World Cup.
"It's the Cook Island dream to make the world cup, like every nation we have our nation's hopes and dreams on our shoulders and to make it would be a dream come true."
He said their biggest match would be up against PNG, who beat them in 2009.
Marsters said he was not sure how much game time he would get but hoped he would start at least one game during the three-match Oceania Cup.
"I'm just glad to be in the team. With the amount of games I think I can make the starting lineup during one or two of the games."
The Cook Island team will spend three days in camp in Auckland before leaving for PNG on July 3 for 10 days.
The team coach, Barry George, is head coach of Manukau Rovers.
Most players in the Cook Island side play their club rugby in New Zealand.