Boating under the influence (federal rule)

Operating the boat & enforcement · Power & sail

Federal law bars anyone from operating a boat while impaired by alcohol or drugs (46 U.S.C. 2302(c)). On a recreational boat the federal limit is a blood alcohol level of 0.08 percent, or the state's own statutory limit on that state's waters, and visible impairment counts at any level (33 CFR 95.020, 95.025).

Commonly missed

Staying under 0.08 percent is not a safe harbor: an officer can find you under the influence at any level if the impairment shows (33 CFR 95.020(c)).
If the boat is not being used only for pleasure, for example when carrying passengers for hire, the federal limit is 0.04 percent and crew members count as operators (33 CFR 95.015(b), 95.020(b)).
Penalty amounts in older guides are out of date: the Coast Guard raises the federal maximums for inflation every year (33 CFR 27.3).

The federal standard

On a recreational boat you are legally under the influence if your blood alcohol concentration is 0.08 percent or more, or if alcohol or drugs visibly affect your manner, speech, movement, appearance or behavior. That second test needs no number (33 CFR 95.020(a), (c)).
Where a state statute sets its own blood alcohol level for boating, that state level replaces the federal 0.08 percent for recreational boats on that state's waters (33 CFR 95.025).
The federal rule does not stop a state from enforcing its own BUI law, so an impaired operator can face state charges, federal action, or both (33 CFR 95.001(a)).
It covers boats on U.S. waters, U.S.-owned boats on the high seas, and foreign boats in U.S. waters (33 CFR 95.005).

Who counts as the operator

The federal rule is aimed at the operator: anyone with an essential role in running a recreational boat that is underway, such as navigating or controlling the engines (33 CFR 95.015(a)).
Underway means not anchored, not tied to the shore and not aground (33 CFR 95.010). State BUI laws can define operating differently, so check your state's law too.
Whoever you hand the helm or throttles to while underway becomes an operator under this rule, so the limit applies to them as well (33 CFR 95.015(a)).

Alcohol, drugs and medicines

Drugs count as well as alcohol. The federal definition of a drug is any substance other than alcohol with known mind- or function-altering effects, including but not limited to controlled substances (33 CFR 95.010).
An intoxicant means alcohol, a drug, or a mix of them, so impairment from medicine, or from alcohol combined with a drug, can meet the observation test (33 CFR 95.010, 95.020(c)).

Testing and refusing a test

A Coast Guard officer, or another officer authorized under federal, state or local law, can direct the operator to take a chemical test of breath, blood, urine or other body fluids when there is reasonable cause (33 CFR 95.010, 95.035).
Reasonable cause exists if you were directly involved in a marine casualty, or if you are suspected of breaking the BUI standard (33 CFR 95.035(a)).
Evidence can be an officer's personal observation of your behavior, or a chemical test (33 CFR 95.030).
Refusing a test an officer directs on reasonable cause can be used as evidence in an administrative proceeding, and you are presumed to be under the influence (33 CFR 95.040(a)). States have their own implied-consent laws.

What can happen

Federally, BUI can bring a civil penalty — the Coast Guard raises the maximum for inflation every year and lists it in 33 CFR 27.3 — or prosecution as a class A misdemeanor (46 U.S.C. 2302(c)).
A boarding officer who finds an apparently impaired operator can end the voyage on the spot as an unsafe condition (33 CFR 177.07(b)).
State penalties are separate and set by each state.

The rules: 46 U.S.C. 2302 · 33 CFR 95.001 · 33 CFR 95.005 · 33 CFR 95.010 · 33 CFR 95.015 · 33 CFR 95.020 · 33 CFR 95.025 · 33 CFR 95.030 · 33 CFR 95.035 · 33 CFR 95.040 · 33 CFR 27.3 · 33 CFR 177.07

Sources (7)

ecfr.gov · law.cornell.edu · ecfr.gov · federalregister.gov · federalregister.gov · navcen.uscg.gov · ecfr.gov

A plain-language summary of federal rules for recreational boats, checked against the rules’ own text and a second source, and written in our own words. It isn’t legal advice. States add rules of their own, and rules change — the links above go to the current official text.