I've been looking at the same thing, but have not yet booked. My impression is that the best options for this purpose tour operators with "Colnago 35" boats. These boats are most commonly used by the operators taking groups on the Blue Cave excursions, including antaresviptours.com and bluecave-split.online.

They are expensive, but these big fast boats make sense if you have a group of 6 or so.