America's Cup holders Oracle Team USA on the charge in Bermuda with Softbank Team Japan at their side.

Oracle Team USA have taken the first steps towards improving their boat for the defence of the America's Cup – and appear to have the continued co-operation of Team Japan in their development drive.

Jimmy Spithill had his American boat out on Bermuda's Great Sound on Tuesday ahead of the opening race of the challengers semifinals.

Oracle have two weeks to tweak their boat while the remaining four challengers scrap it out to see who will come through to contest the Auld Mug.

It seems the bulk of the development work will be done during the night by the shore crew to allow the testing to go on during the day by Spithill and his crew.

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RICARDO PINTO / ACEA 201 Team Japan's crew takes a soaking as they race Artimis off Bermuda on Tuesday.

Having someone to gauge the effectiveness of their constant changes will be crucial.

If Tuesday is anything to go by, that boat will be Team Japan who have had a design and information agreement with the defenders since joining this cycle of the Cup.

It's an unholy alliance, going against the traditions of the cup that rarely sees a challenger help a defender.

On Tuesday that was exposed. Oracle lined up for what looked to be a serious speed run after hooking up with Japan.

That came while Japan were out on the water, warming up for their challenger semifinal against Sweden.

Team New Zealand and Ben Ainslie Racing were also on the water at the time, preparing for the semifinal on the other side of the challengers draw.

RICARDO PINTO / ACEA 2017 Team Japan's unofficial duel with Oracle was unusual, in that a challenger rarely helps a defender.

The interest from here will be to see if Oracle and Japan have regular hook-ups like today's.

Oracle don't have a second boat to do in-house testing while their potential rival for the match gets in serious racing.

Earlier in the week Spithill indicated that Oracle had called in their New Zealand boatbuilders to help make their AC50 more competitive for the final.

After their speed run with Oracle, Dean Barker's Team Japan showed improved upwind speed to beat Sweden in their opening semifinal but then saw Artemis Racing bounce back to tie the series 1-1.

Team New Zealand gained both points in the other semifinal when the British broke down in the first race and couldn't repair their wingsail in time to start the second race.

The next two races in both semifinals series are due to be sailed in increased winds on Wednesday.