Slack water.
Anchor set.
Dive it.
A free navigation app for dive boats with NOAA slack-tide windows, live current vectors at dive sites, anchor alarm, NDBC buoy wind and wave, and NEXRAD weather radar. For the site you love, and the one you haven't tried yet.
Plan a dive day ← other watersThe window, measured.
NOAA CO-OPS current predictions show exactly when the water stops moving at your site. ChartNav surfaces the slack-water window plainly — start, end, duration — so the dive plan writes itself.
Max current, direction of set, and the transition between ebb and flood all render on the current curve. The nearest station auto-locks to your GPS position. No more guessing from a paper tide book.
Divers down. Boat held.
Drop a radius. ChartNav watches your GPS against it. The moment the hook starts to drag, the alarm sounds — even if you've drifted off while divers are still below.
Runs in your browser or the installed PWA, works with the screen off. No app-store subscription, no drain on the dive-boat iPad. Pair it with a hardware horn via phone audio output.
Every site you've ever loved.
Save wrecks, reefs, and natural sites as waypoints with notes — depth, orientation, vis notes, access. Your private library lives on your device. Export as GPX to your plotter or your buddy's.
Weather and tide context renders right on the site marker. Open a site, see the forecast, see the current, decide.
Everything between briefing and pickup.
Slack windows
NOAA CO-OPS current predictions with plain slack start, end, and duration per station.
Current vectors
Arrows show set and drift at the site and around it — up-current entry points become obvious.
Anchor alarm
Drift-circle watch with audible alarm. Keeps the boat while divers are down.
NEXRAD radar
Level-2 + NIDS. See what's coming before divers splash.
Wave & wind
NDBC buoy wind, gust, wave height, and period — live from the nearest station.
Dive-site waypoints
Private library of wrecks, reefs, and natural sites with notes, depth, and access info.
AIS awareness
See every boat approaching the site. Dive flag stays put, you still see who's coming.
Installs offline
Progressive Web App works when cell signal doesn't. Cache your library, take it out.
Questions from the dive platform.
Everything that comes up at briefing. Answered.
How does ChartNav help dive boats find slack tide?
NOAA CO-OPS current predictions render as a curve, and the slack window is highlighted with start, end, and duration. The nearest station auto-locks to your GPS, so you see the window for the site you're actually diving.
Does the anchor alarm work while divers are down?
Yes. Set a drift radius, keep the tab open (or the installed PWA), and the alarm sounds on GPS drift. It runs on any phone or tablet with no App Store install.
Can I mark and save dive sites privately?
Yes. Drop waypoints with notes. Libraries live on your device in browser storage and never leave unless you export as GPX.
What weather sources does ChartNav use for dive planning?
NOAA NEXRAD Level-2 and NIDS, NWS alerts and dense-fog advisories, NDBC buoy wind and wave, GOES satellite, and live lightning feed.
Is ChartNav free for commercial dive charters?
Yes — no subscription, no account, no commercial-use surcharge. AIS and NOAA data are public; ChartNav makes them usable.
Can I see other boats approaching my dive site?
Yes. Every AIS-equipped vessel within range renders on the chart with live position, speed, and heading — useful for managing the dive flag radius and pickup zone.
Call the window. Drop in.
Free. Browser-based. No App Store. Your phone or helm tablet, a chart, and the whole dive-day briefing.
Open ChartNav