John Key and Malcolm Turnbull's 'bromance' continued today, with the trans-Tasman leaders enjoying a kayaking trip on Sydney Harbour.

The pair donned their life jackets and hit the harbour after a day of negotiations - including over citizenship rights for Kiwis living in Australia - in Sydney.

Key posted a picture to Twitter of him with the Australian PM, each resting an arm on the other's stylish kayaks.

"Enjoying the beautiful Sydney harbour with @TurnbullMalcolm," Key wrote.

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In the spirit of trans-Tasman friendship, Turnbull retweeted his mate's message.

The kayaking trip comes after an overnight stay for Key and his wife, Bronagh, at Turnbull's mansion at Pt Piper, which is estimated to have a value of $60 million.

The stay was dubbed "pyjama diplomacy". Before the sleepover, Key spoke of the fact he was looking forward to enjoying some fine Australian red wine.