Well, we had sun and used the go pro to look under the boat and found a big tangle and ball of weed on the keel and sail drive. We backed down really hard and cleared it (confirmed with go pro again) and are now able to reach our target speeds. There is much rejoicing. Even though we tried to back down two other times, I suspect that it had been there since our channel crossing Monday morning.
Today was a day full of dolphins and a European storm petrel, a life bird for Hannes. And a double submarine sighting. They called one of the other race boats as they were quite close.