Ivan Aivazovsky

Supposedly he painted the sea from memory indoors rather than out in front of it, and turned out thousands over a lifetime — storms and wrecks by the dozen, selling about as fast as he could make them.

Sailors reckoned waves arrive in runs and the ninth one is the one that finishes you — supposedly that's where the name comes from. He was a navy painter by trade and, from what I've read, worked from memory in the studio rather than out in front of the water.