keira knightley pirates of the caribbean cleavage

Keira Knightley's treasures were far from buried in "Pirates of the Caribbean." Photo: Walt Disney/Courtesy Everett Collection

Thar she blows!

The ship will be a little short on flotation devices in the fourth installment of "Pirates of the Caribbean," as director Rob Marshall has banned breast implants from the set, according to the Daily Mail.

The franchise's new helmsman has reportedly issued a casting notice calling for "beautiful female fit models. Must be 5ft 7in - 5ft 8in, size 4 or 6, no bigger or smaller. Age 18-25. Must have a lean dancer body. Must have real breasts. Do not submit if you have implants."

Marshall will also be hosting a "show and tell" day to make sure any rogue implants walk the plank, reports the paper.

But don't worry, fellas. There will be plenty of "treasure chests" on display in "Pirates of the Caribbean: On Stranger Tides" -- just not fake ones.

For starters, Keira Knightley -- who reportedly had to have cleavage painted in during the previous movies -- will be replaced by curvaceous leading lady Penelope Cruz.

"In the last movie there were enhanced breasts to give that 18th-century whoreish look and men were pretty well padded too and no one worried," a former casting agent told the Daily Mail. "But times are changing and the audience can spot false breasts."

Yes indeedy. But rounding up a crew of Hollywood actresses with nary a drop of silicone in them? You'd have a better chance of plundering Long John Silver's booty.

They can always cast "real" women, whose busts show no sign of decreasing in size anytime soon.