826 nautical miles in 24 hours!!! that's what managed François Gabart 4 days ago while on his attempt to beat the circumnavigation record. He had already beaten his personal speed record doing 46K on his Maxi trimaran. I remember that the boat designers estimated max speed to be 42k and that many thought that would be too optimistic!
We are not talking about America's cup boats racing in protected waters but about ocean sailing and that's a completely different affair. He is going so fast on extreme conditions that many knowledgeable sailors are starting to be concerned about safety. But that's François Gabart, I have heard the same story when he was leading the Vendee Globe at an incredible pace, leaving behind Armel Lecleash.
Anyway he was sensible to those concerns and has diminished the speed. Just look at the conditions and what he calls reduced speed LOL. He has already an advance of almost 700nm over the previous record (from Coville)