This is absolutely insane. Apparently, there are people so rich that, not happy with having their own megayacht, get themselves a huge support ship to carry giant speedboats, sailboats, helicopters, and even submarines. That's what the Sea Axe is.
The Sea Axe comes in 37, 51, or 67 meters flavors, and it's capable of carrying other ships, fuel, and supplies. It has transatlantic range and can travel at a top speed of 28 knots. [James List]