The Gulf Stream is a river within a sea but far from running true and straight it loops and whirls its way across the Atlantic. And the yachts taking part in leg 7, Annapolis to La Rochelle, of the Volvo Ocean Race will step straight onto this escalator the moment they leave Chesapeake Bay and, if they have their tactics right, not step off it until they approach the finish.

This picture clearly shows the direction and speed of the Stream in the West Atlantic on 26 April. Get it right and it will boost SoG by as much as two knots. Get it wrong and it will have the opposite effect, making differences in boat speed between two boats, one in the Stream, the other in a counter eddy, as much as a race winning (or losing) 4 knots. Small wonder, then, that some boats will be carrying two navigator/tacticians. And small wonder that these same tacticians have been in huddles with Stream experts for several days now.

If you want to check the Gulf Stream on a daily basis, go to

ftp://ftp.deos.tudelft.nl/pub/altim/gulfstream/