Clad in this year's beige "silly shirts", the 15 Pacific Island Forum leaders including New Zealand Prime Minister John Key sailed to Eneko Island, a distant part of the main atoll Majuro, on Thursday morning for discussions away from officials and media.
Australia's representative, Mental Health Minister Jacinta Collins, flew in late on Wednesday night ahead of the retreat, where she's representing the government while other ministers focus on this weekend's general election.
The Marshall Islands has chosen climate change as the theme of this year's forum, as it and other low-lying Pacific states become increasingly desperate for solutions to escape rising waters, severe weather and ocean acidification.
Ahead of the retreat, Mr Key said he was looking forward to discussions the Pacific way, culminating in a communique outlining a united position on a number of issues.
Mr Key and Senator Collins will face scrutiny over their countries' meagre carbon emissions reduction targets, which smaller nations want them to bolster.
Both countries say big emitters such as the United States, China and India also need to commit to climate change solutions.
Leaders will endorse the new Majuro Declaration, a statement urging countries to set bold carbon reduction targets and take meaningful action to combat climate change.
On Friday, they'll take the declaration to a post-forum dialogue with big emitters.
Leaders will also discuss the situation in Fiji, which remains suspended from the forum until it holds democratic elections due to take place in September next year.
Ahead of the retreat, Mr Key indicated New Zealand's stance on Fiji is softening, saying its new constitution, including immunity for coup leaders, is not perfect, but the Pacific must look to the future - a view shared by small island leaders at a series of press conferences ahead of the retreat.
