OBS Cheat Sheet 2026

The 30 highest-yield OBS facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. A nautical chart shows a depth of 15 feet at Mean Lower Low Water (MLLW). What does this mean for your planning? → The depth will never be less than 15 feet
2. Which federal agency is primarily responsible for enforcing boating safety laws on US navigable waters? → The US Coast Guard (USCG)
3. What does a downed skier in the water display to alert other boaters? → A raised ski or arm above the water
4. Which of the following best describes a 'documented vessel' under federal law? → A vessel federally registered with the US Coast Guard instead of a state
5. Which action best demonstrates defensive boating when another vessel is acting unpredictably? → Slow down, give wide berth, and be prepared to stop
6. How does collaboration enhance Traffic Laws & Regulations in Online Boating Safety Certification? → It brings diverse perspectives and improves outcomes
7. How does cold water affect an intoxicated person who falls overboard? → It can accelerate hypothermia because alcohol dilates blood vessels, increasing heat loss
8. A vessel is planning a coastal trip and must cross a shipping lane. What is the safest crossing procedure? → Cross at a right angle (90°) to the traffic flow as quickly as possible
9. What is the correct way to read a chart's compass rose? → The outer ring shows true north; the inner ring shows magnetic north
10. What is the purpose of a 'float plan' in defensive boating? → To inform someone ashore of your trip details so they can alert rescuers if you're overdue
11. When backing a single-engine outboard boat, the stern tends to swing in which direction first? → In the direction the propeller rotates (typically to port for standard rotation)
12. What do five or more short blasts on a horn or whistle mean? → Danger or doubt about the other vessel's intentions
13. What is the danger of turning a boat engine on with people near the stern in the water? → Carbon monoxide exhaust at the stern can incapacitate or kill swimmers
14. How often should you inspect your boat's steering cable or hydraulic steering system for proper operation? → At the start of every boating season and periodically throughout the season
15. When a power-driven vessel is overtaking a sailing vessel in a narrow channel, who has the right of way? → The overtaken vessel (the sailing vessel), because the overtaking vessel must keep clear
16. What signal should a power-driven vessel sound when leaving a dock with vessels nearby? → One prolonged blast
17. Under what condition is it safest to refuel a boat with passengers aboard? → Passengers should disembark and move away from the vessel during fueling
18. Research shows that a boat operator with a BAC of 0.10% is approximately how many times more likely to be involved in a fatal accident than a sober operator? → 10 times more likely
19. What is the purpose of a Marine Sanitation Device (MSD) Type I? → It treats sewage to reduce bacteria levels below a legal threshold before discharge
20. What should be done if a boat capsizes in open water? → Stay with the boat and signal for help
21. How often should a boat’s engine and fuel system be inspected? → Before every trip
22. What is a 'range' in coastal navigation? → Two objects aligned to indicate a safe navigational track
23. What does a flashing yellow buoy or light indicate on US waterways? → A cautionary area such as a traffic separation scheme
24. How far offshore must a vessel be before legally discharging untreated sewage in federal waters? → 12 nautical miles
25. A vessel displaying a black cylinder shape by day is indicating what condition? → The vessel is anchored
26. When should you activate an EPIRB (Emergency Position Indicating Radio Beacon)? → When your vessel is in grave and imminent danger
27. How should a vessel's name and hailing port be displayed on a documented vessel? → On the stern in letters at least 4 inches high and on the hailing port below
28. Under the Inland Navigation Rules, vessels in a head-on situation must: → Both vessels alter course to starboard to pass port-to-port
29. What is the primary purpose of DSC (Digital Selective Calling) on a VHF radio? → To automatically send a distress signal with GPS position to rescuers
30. What should a boater do when approaching a sailing vessel under sail? → Give way to the sailing vessel