Diane Duane:
(born May 18, 1952).
American science fiction and fantasy author, long based in Ireland. Her works include the Young Wizards young adult fantasy series and the Rihannsu Star Trek novels.

Do it now and avoid the June rush! Fear death by water!

“Fear death by water” — T.S. Eliot, “The Waste Land” (1922)
The line is spoken by the clairvoyant Madame Sosostris in the opening section of Eliot’s modernist epic. She pulls the card of the Drowned Sailor from her tarot deck and warns the narrator, “Fear death by water.” The prophecy is then fulfilled in Section IV, “Death by Water”, where Phlebas the Phoenician sailor has drowned, his body yielding nothing but decay — no resurrection, no transfiguration. The section’s point is that the physical reality of death triumphs over everything.
The phrase carries layers of meaning. The poem’s short “Death by Water” section turns on opposites: profit and loss, age and youth, Gentile and Jew — all rendered immaterial by death.
Author: As for: “Do it now and avoid the June rush! Fear death by water!” That is attributed to Diane Duane, the science fiction and fantasy author best known for the “Young Wizards” series. The full quote is: “Do it now and avoid the June rush! Fear death by water!”
It appears to be a humorous, sardonic quip — likely a winking allusion to Eliot — playing on the idea of procrastination and urgency. The “June rush” is a playful bit of mock-advertising logic (“act now!”), punctuated by the sudden, darkly absurd Eliot reference. It reads less like a life lesson and more like dry, literary wit. It’s not an “idiom” in the traditional sense, but more of a quotable, ironic one-liner.
So in short: the ‘phrase’ “Fear death by water” is Eliot’s (1922); the ‘quip combining it with “avoid the June rush”‘ is Diane Duane’s.