Ship Arriving Too Late to Save a Drowning Witch was released in May 1982, but is a collection live recordings of shows from September to December 1981.1 The cover of the Frank Zappa album was done by Roger Price (not by Zappa, as help im a rock nodes), and actually looks more like this:
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("Ship arriving too late to save a drowning witch" is written across the bottom of the album cover.)
Roger Price is the author of a delightful little book called Droodles (ISBN 0-8431-0009-5), which has dozens of these simple, hilariously-captioned drawings (like "Famous Scientist Seen Through Microscope" and "Germs Avoiding Friend Who Has Caught Penicillin"). Price also notes about the droodle in question: "This, of course, appears to be 'A Mother Pyramid Feeding Its Child,' but it isn't." My edition of the book was published in 1978 by Price/Stern/Sloan; copyright dates start in 1953 and end in 1966.2 Some say Zappa chose the art because it resembles the top halves of the first two letters in his last name.
The album features Steve Vai on "Impossible Guitar Parts," and Moon Unit's part in "Valley Girl" is so convincing, I can't even listen to it. Moon Unit made up the lines as she went, recording into a mike in the middle of the night under Dad's watchful eye. Moon later said she's not really anything like a valley girl, she used the impression to make people laugh.1
References:
1: Ship Arriving Too Late to Save a Drowning Witch: http://globalia.net/donlope/fz/lyrics/Ship_Arriving_Too_Late_To_Save_A_Drowning_Witch.html
2: Roger Price, Droodles. Price/Stern-Sloan Publishers Inc., Los Angeles: 1978.