Hit Giant's Deep REALLY fast to break through the current. I locked on and went away to about 170km then turned around and accelerated straight towards it. Make sure to keep the dotted lines to a minimum while moving towards otherwise you might fly past it; they show when you've matched the heading of your target. Once I got below the current (but not below the electric core) it unlocked. Requires a tiny bit of luck since if there's an island or the probe launcher in the way you won't be able to avoid it at the speed you require.
Edit: This may also work. Fly into a counter clockwise vortex. Those ones push you down. I already had achievement from first thing so not sure if this counts.
Edit: Sounds like cyclone method doesn't work, have to use speed method.