Shipwrecked Sailors Raft?

A shout from Emily on the foredeck brought us running to see a black raft about 8'square drift past low in the water. I pressed the Man Overboard alarm to mark its location and as the piercing alarm started it's regular and unstoppable noise, we rolled in Genoa and staysail, started the engine and motored back upwind for quarter of a mile to check the raft for signs of life.

As we approached we could see that it trailed a thick rope with a floating light on the end. It must be an oceanographic drifter collecting information about currents, salinity, temperatures and even wave height. I will send this photo to an oceanographer contact to see if it can be identified.

I finally found out how to cancel the alarm noise, and we reshape our course, heading slightly south to follow the latest wind predictions.

I then put out an All Ships alert by VHF to advise of the floating hazard to navigation. The yacht Acapella five miles astern of us, seems to have switched off their radio so I hope they don't hit the raft. It looks rather solid. We came very close to colliding with it.