The Prime Minister has given an undertaking to help Indonesia fight back against illegal fishing by overseas poachers - including the Chinese.
The Indonesian government claims illegal fishing is costing the country billions of dollars a year.
The situation is so tense they've even resorted to blowing up vessels caught fishing illegally.
One of the main culprits is said to be China, whose aggressive territorial behaviour in the South China Sea has been criticised by international tribunal, The Hague.
"Look I think there's been some issues around potentially fishing and disputes over fishing and everyone can see what they've been doing in terms of reclamation of land," Mr Key said.
But he is quick to point out New Zealand's steering clear of the controversy.
"New Zealand's point of view is really to say 'look we don't take sides on that' and see if the parties can try and find a way through."
Earlier this week the Indonesian government announced it would expand its fisheries monitoring base in the Natuna Islands where much of the illegal fishing takes place. It would mean expanding the port and increasing personnel.
New Zealand's role will focus more around information sharing which could prove crucial with such a large area to cover.
"It's really just trying to give them confidence about how to protect their fisheries," Mr Key says.
Mr Key will certainly be celebrating a successful trip to Indonesia, but his focus now quickly shifting to US Vice President Joe Biden who he'll host in back home in New Zealand on Thursday.