Every light, flag and buoy, one glance away.
Ahoy is a pocket field guide for sailors. Ship lights, signal flags, buoys, weather and VHF, all offline, no account, free.
- Free
- Fully offline
- No account
- No ads
“There's never enough learning at sea, and Ahoy is a brilliant way to keep at it.”
“It's never been easier to recall what I need for another safe adventure.”
“With Ahoy in my pocket, I feel as seaworthy as the boat I'm on.”
What's inside
A field guide for the moments you need an answer fast.
Ship Lights
Identify vessels at night by their light pattern, shown from every angle as glowing schematic diagrams.
Signal Flags & Marine Alphabet
All 36 flags with their meanings, Alpha to Zulu, plus the phonetic alphabet.
Buoys & Day Shapes
Lateral and cardinal marks with the shapes each can take, plus the cones, balls and diamonds and what they signal.
Weather
The Beaufort scale with real sea-state photos, and clouds with what each one means for your weather.
2 Bft
6 Bft
10 BftSound & Radio
Sound-signal patterns for every condition, and ready-to-read VHF scripts: Mayday, hailing a vessel, radio checks.
Dictionary
Searchable sailing jargon, from abeam to windward.
Education
Train your eye
Ahoy is built for quick lookups, but when you want to go deeper there is an Education tab.
Endless recognition drills, exam style: a light or a day shape appears, you name it, you learn. Ship lights and day shapes now, more on the way.
And so much more ✨
- Cardinal marks
- Lateral marks
- Isolated danger marks
- Safe water marks
- Special marks
- Day shapes
- Cloud types
- The Beaufort scale
- Phonetic alphabet
- Sound signals
- VHF radio scripts
- IALA A & B regions
- Cardinal marks
- Lateral marks
- Isolated danger marks
- Safe water marks
- Special marks
- Day shapes
- Cloud types
- The Beaufort scale
- Phonetic alphabet
- Sound signals
- VHF radio scripts
- IALA A & B regions
Frequently asked questions
Everything you need to know about Ahoy.
Hey 👋 I'm Krzysztof, and I built Ahoy because I sail for fun and got tired of nodding along when the skipper pointed at a light or a buoy I couldn't name.
The apps I found wanted to turn me into a student, all flashcards and long courses. I just wanted something I could pull out on deck, check in a few seconds, and put away. So I built it.
My hope is that Ahoy makes you feel a little more at home on the water.
(PS you can find the rest of my work at kristof.pro, or the occasional note on Substack.)
Krzysztof Przekwas
Ready to cast off?
Ahoy is free, works offline, and asks for nothing. Download it and see.
Download on theApp Store