The Coast Guard's first "drunken boating" rules take effect today, but a $100 million budget cut may jeopardize their enforcement, officials said.

Federal law directed the secretary of transportation to set the standards for determining drug and alcohol intoxication aboard commercial and pleasure vessels, said Sean Connaughton, a Coast Guard official.

Under the rules, a pleasure boater with a .10 percent blood-alcohol level will be considered drunk, Connaughton said, while for a commercial seaman operating a vessel, the standard is .04 percent. Where states have set standards, "we will enforce that standard," he said, noting, "Most states have a .10 standard."

"For drugs, we have set a behavioral standard," he said. "An individual is considered intoxicated {by drugs} if the effect of the intoxicant affects the person's manner, disposition, speech, muscular movement, general appearance or behavior."

He added, "The new rules apply to everyone on U.S. waters -- to foreign vessels coming in, boaters on the Potomac, all vessels under federal jurisdiction -- which is practically everything" under the Constitution's "navigable waterways" clause.

But Coast Guard spokesman Nicholas Sandifer said enforcing the new rules will not be easy because of a $100 million cut in the Coast Guard's operating budget for fiscal 1988, which began Oct. 1.