Know the signaling devices required for vessels between 20 and 100 meters under COLREGs.

Vessel Signals: Why a Whistle and Bell Matter More Than You Think

If you’ve ever stood on a deck listening to the morning sea, you know how quiet it can feel—until a nearby vessel suddenly breaks the hush with a sharp blast or a hollow bell that cuts through the spray. Those sounds aren’t just noise. They’re a lifeline. For ships between 20 and 100 meters long, a whistle and a bell aren’t optional accessories; they’re required tools that help everyone share the water safely. Let me walk you through what that means, in plain language, and why it matters in real life.

What the rules actually demand, in plain terms

Here’s the bottom line, cut to the chase: vessels from 20 to 100 meters must carry two sound-signaling devices—a whistle and a bell. That’s the core requirement you’ll see codified in the COLREGs framework, the rules that govern navigation etiquette and safety at sea. The whistle is the intentional audible signal you can blow when you want to warn, warn again, or indicate your intention to change course. The bell serves as a clear, steady presence—especially useful in fog, mist, or any reduced visibility where other sounds blend together.

A foghorn, a gong, or other signaling devices aren’t automatically mandatory for this size range. They can appear in certain situations or regions, but the basic requirement for a vessel in this length category is simply the whistle and the bell. If you’ve been wondering about the “extra” devices, think of the whistle as your voice—clear and directional—and the bell as your steady beacon that’s hard to ignore when visibility drops.

Whistle and bell: what each one does, and why both matter

• The whistle: Think of it as your communicative voice over water. A properly tuned whistle produces distinctive blasts that other mariners can recognize at a distance. You’ll use it to signal changes in course, to indicate your right of way, or to make your presence known in situations where a quick, audible cue matters. It’s particularly vital in scenarios with limited visibility, where visual signals are unreliable.

• The bell: A bell has a different, complementary role. It’s a passive, consistent sound that helps others locate you when the air is thick with fog, rain, or spray. Bells cut through background noise in ways a voice signal can’t, especially when your vessel is moving slowly or is maneuvering in close quarters. When others hear a bell, they get a clearer sense of your vessel’s presence and timing.

In practice, your whistle and bell work together like a two-part chorus. The whistle says, “I’m here, and I’m about to do something,” while the bell says, “I’m present and moving—please take note.” The combination reduces ambiguity and buys you precious seconds in crowded waters or tricky weather.

How signaling fits into the everyday life of a vessel

Let’s anchor this with a few real-world moments, because theory helps, but practice saves lives.

• Crossing situations: If you’re approaching a crossing with another vessel that has the right of way, you might use a short blast on the whistle to announce your approach, followed by a longer blast if you intend to alter course. The bell’s steady tone isn’t a replacement for this, but it reinforces your presence, particularly if the other vessel is slower to detect audio cues.

• Overtaking: When you’re overtaking or being overtaken, the COLREGs emphasize clear signaling. The whistle provides explicit instruction signals, while the bell remains a persistent reminder of your vessel’s location as you maneuver.

• Fog and reduced visibility: In a foggy stretch or along a coastline where visibility dips, the bell becomes especially important. The sound travels in the damp air differently, and a bell’s regular chime can help others gauge your proximity and direction even when the visual cues are weak.

• Nighttime and splashy seas: At night, a light is essential, but sound signals still play a key role. The whistle helps with immediate warnings, and the bell offers a constant audible cue for nearby vessels that might not see you until they’re very close.

A few practical notes you’ll want to keep in mind

• Equipment integrity matters: The best signal is the one you can actually deliver. Regular checks are part of standard seamanship. Test the whistle so it’s loud enough to carry the distance required by your operating area, and ensure the bell is exposed to minimize muffling from decks, ropes, or other gear.

• Accessibility is non-negotiable: Your signaling devices should be easy to reach and operate. If your crew needs to search for a switch or a lever in an emergency, you’ve just added seconds that could make a difference.

• Redundancy makes sense in rough seas: If you’re operating in regions with heavy traffic or variable weather, having a simple backup method (like a second signaling horn or an alternate bell) can be a prudent precaution. It’s not about overdoing it; it’s about reliability when it counts.

• Familiarize the crew with procedures: Signals aren’t just about one person pressing a button. The whole team should know when and how to use the whistle and bell, and what responses to expect from nearby vessels. Clear, practiced routines reduce chaos when visibility drops or weather worsens.

Common questions—answered in plain language

• Do all vessels between 20 and 100 meters need a foghorn or additional signaling devices? Not necessarily. The core requirement is a whistle and a bell. A foghorn or other devices may be used as extra signaling, depending on local rules or specific situations, but the standard kit for this size range is the whistle and bell.

• When exactly should I use the whistle? In general, use it to indicate changes in course, to warn other vessels of your approach, or to signal your intentions in traffic situations. Short blasts can communicate urgency; longer blasts can indicate a deliberate action like turning to starboard or port.

• Is the bell enough by itself in fog? The bell alone isn’t a substitute for a whistle. The two signals complement each other. In fog or heavy rain, the bell gives you audible presence, while the whistle conveys your intended action.

• Can you use a modern electronic horn instead of a traditional whistle? The COLREGs focus on sound signaling capability more than the exact device. If an electronic horn meets the required sound pattern and can be heard at the necessary distance, it can satisfy the intent. The key is that the signal is clear, distinct, and reliable.

Why this tiny pair matters so much in practice

Here’s the thing: safety at sea hinges on shared expectations. When two vessels approach a narrowing channel or a crowded anchorage, everyone’s first instinct should be to assume that the other is aiming to avoid a collision, not to blame. The whistle and bell help establish that mutual assumption quickly. A whistle blast can communicate “I’m turning left” or “I’m slowing,” while the bell confirms “I’m here, near you, and in front of you.” Those little sonic cues prevent misreads, and misreads are where accidents begin.

A quick note on maintenance, because good signal gear is a quiet investment

• Check monthly: run a quick test of the whistle and inspect the bell for any corrosion or loose fittings.

• Cleanliness matters: salt spray and barnacles don’t mix well with sound devices. Keep the mouths and the bell clean so sound travels cleanly.

• Replace when needed: if the tone becomes muted or the mechanism sticks, replace or service before you rely on it in rough conditions.

• Log the checks: a simple log helps you track the device’s health over time, which is useful during inspections or when something unexpected happens.

Bringing it all together

The rule for vessels in the 20–100 meter range is straightforward on the surface, but its implications run deep. The whistle gives you a clear voice across distances and through weather. The bell provides a constant, recognizable presence when visibility is compromised. Together, they’re a compact toolkit that supports safer navigation, smoother near-shot interactions, and fewer tense moments in busy waters.

If you’re charting your path through the COLREGs and you want a mental shortcut, remember this: whistle for action, bell for presence. Use them together, practice them in calm conditions, and keep them ready for the moments when weather or traffic tightens the sea around you.

One last thought: boats are about people as much as they are about steel and sails. Sound signals aren’t just lines in a book; they’re courteous, practical gestures that tell other mariners, “I see you, I’m here, and I intend to stay on a safe course.” In the end, that shared courtesy is what keeps the water safer for every voyage.