Word of a whale-plinking incident on the high seas has filtered back to Washington, setting typewriters a-clicking faster than one can say, "Thar she blows."

In a letter to Defense Secretary Caspar W. Weinberger, Sen. William Proxmire (D-Wis.) demanded a vigorous investigation into allegations that two Navy officers fired as many as 150 rounds of rifle ammunition at a group of whales during target practice in the Indian Ocean last year.

"I am sure you will agree that these allegations, if they are true, constitute a deplorable incident," Proxmire wrote. Aside from being bad form, shooting at or otherwise harassing whales in U.S.-controlled or open waters is a violation of federal law.

According to interviews collected by Proxmire's staff, the incident allegedly took place last October aboard the USS San Jose. As Proxmire relates it, the supply ship was cruising in the Indian Ocean when it stopped to conduct "gunnery practice," which in this case consisted of firing an M14 rifle at a metal barrel that had been tossed overboard.

"While the shooting was going on, a pod of about a dozen whales and several baby calves swam into the target area," Proxmire wrote. Witnesses told his staff that the whales were visible from the bridge, but that the ship's captain and first lieutenant kept firing.

A Navy spokesman in San Diego said the service had been aware of the allegation, thanks to a Defense Department hot-line tipster, and had appointed an investigating officer in August.

"We're waiting for his report," said Lt. Cmdr. Ron Morse. It appears that Proxmire will have to wait as well.

"We have a very well established procedure and feel to deviate from that for any reason would not be productive," Morse said. "We think we're doing the right thing rather than trying to find a quick solution to a potentially ugly problem."