Submarius
The spearfishing app for conditions, wrecks, reefs and safety.
Swell and wind. The tide, and which way the current is setting. Water temperature, a visibility estimate, where the wrecks and reefs sit and the depth around them, the fish recorded nearby, and someone watching for you to come back. Submarius puts all of it in one app, for the spot you're diving.
The conditions, read for a dive.
Spearfishing is the default mode, so Today opens with the tiles a spearo looks at first. Moon phase, sunrise and sunset sit alongside them. Tap any hour for the full detail, including the second and third swell and a radar loop of the last hour.
Swell height and direction, plus the wave height you'll meet. Near the coast the headline is a shore break estimate, with the offshore height and period under it. Where a NOAA or CDIP buoy within 60 km is reporting, the wave height is blended with its reading.
Speed and direction, hour by hour, so you can see whether the calm morning holds or the afternoon breeze arrives early.
Rising, falling or slack, the next high or low, the range, and a 24 hour curve. Within about 50 km of a US station it uses NOAA predictions. Everywhere else it uses a global tide model.
Drift in knots, the direction the water is setting toward, and the next slack when the model shows one in the next 12 hours, read from the current forecast rather than the tide table. It comes from a global ocean model with cells about 25 km across, so a headland or a channel can run a lot harder.
Sea surface temperature, with the air temperature underneath, so you can pick the right wetsuit before you leave the house.
A model estimate of how far you'll see, shown as an approximate distance with a confidence percentage beside it. The confidence tells you how much weight to give it.
The 3 hour stretch with the highest average score in the next 24 hours. Plan the session around it instead of judging the whole day by one number.
Wind, waves, swell, tide, moon and the visibility estimate roll into one 0 to 10 rating for the day, labelled PRIME, GOOD, FAIR, CHOPPY or ROUGH, with every factor behind it one tap away. In Spearfishing, visibility carries the most weight. Water temperature and current are there for you to read and don't move the rating. A thunderstorm hour caps the rating, and in the US so does an active National Weather Service warning. If you're going out by boat, sailboat, kayak or SUP, add that too, and the rating is only as good as the weaker of the two.
Reefs, wrecks and depth on one map.
The reefs and wrecks layer merges NOAA electronic nautical charts, Florida FWC artificial reefs, BOEM platforms in the Gulf of Mexico, OpenStreetMap and a Wikipedia derived wreck list into one set of pins. Tap a wreck and you get the seabed depth beside it (a labelled estimate when no source reports one), the least depth over it where a chart sounding exists, how many sources agree, and the conditions at the site. Pin it to your spots or set it as your location. All four layers below are Pro.
More than 380,000 mapped reefs, wrecks, obstructions, dive sites and platforms as of August 2026. Tap one for the depth beside it and the conditions at the site.
Depth shading and contours worldwide, with NOAA BlueTopo relief in US waters.
The official US nautical charts, with soundings and depth contours. US waters only.
Live coral, sand, rubble and seagrass, mapped across tropical reef waters.
The fish near you, and the rules for them.
The Fish tab lists the species recorded near your spot, from iNaturalist and OBIS observation records, with iNaturalist photos and WoRMS names and habitat. Where we have the rules, they sit on the species card with a link back to the agency:
- California. CDFW rules for 22 species, with license information.
- Florida. FWC rules for 22 species.
- Atlantic highly migratory species. Federal Atlantic rules for 36 species of tuna, billfish, swordfish and shark, for the US Atlantic, Gulf and Caribbean.
Rules attach only when your pin resolves to a place in the US, and state rules only in California or Florida. So a pin on an offshore reef, even a few miles out, can come back with no rules at all. The app doesn't mark marine protected areas. Confirm limits and seasons on the agency's site before you dive.
Safety tools, free for everyone.
File a plan with a "back by" time and pick who watches. If you haven't checked in by then, our server alerts them, by push if they have the app and by email if they don't, so the alert still goes out when your phone is dead or out of signal. SOS goes to your contacts after a 5 second countdown you can cancel, and needs a moment of signal to send. While a plan is open, the app sends a surface position every 5 minutes as long as it's on screen, so your watchers know where to start looking. It needs a free account. It never contacts the coast guard or other authorities, and it doesn't send text messages.
With Spearfishing as your mode, Today shows the shark species recorded in the area from OBIS records, each with a diver risk tier and labelled as awareness, not a live feed. It also shows community sightings from the last 48 hours within 50 km. Signed in users can report a sighting, and people with the iOS or Android app within 25 km get a push. Reports are unverified until they're reviewed.
Record the trip with no signal.
Start a trip and the app records your GPS track on the phone, with or without signal and without an account. It records while the app is open on screen and doesn't track in the background. Exporting a trip as a GPX file is Pro.
Your spots stay on your phone.
Press and hold on the map to drop a spot and tag it as a reef, wreck, kelp bed, ledge, pinnacle or launch. Spots are private, there's no limit on how many you keep, and they're stored on your device. There's no public spot map and no community feed to leak them to. With Pro you can back up and sync spots and trips between devices, and they're encrypted on your phone before they upload.
Spearfishing conditions, spot by spot.
Open a location for its spearfishing conditions, or see every spot we cover.
Common questions.
Spearfishing is the default mode, so Today opens with swell, waves, wind, tide, current drift (and the next slack when the model shows one), water temperature, a visibility estimate with its confidence figure, moon phase, sunrise and sunset, and the best 3 hour window in the next 24 hours. Wind, waves, swell, tide, moon and the visibility estimate roll into a 0 to 10 rating for the day, with visibility weighted most in Spearfishing. Water temperature and current are there for you to read and don't move the rating. Around that sit a Pro map of reefs and wrecks with depths, the fish recorded near you with California, Florida and Atlantic highly migratory species rules where they apply, Safety Watch, a shark awareness card, trip recording and private spots.
Today's 0 to 10 rating, every tile for today, the hourly strip for the next 12 hours, the best 3 hour window, the Fish tab with regulations, trip recording, unlimited private spots and every safety tool are free. Pro adds forecast days 2 to 8, the Pro map layers (reefs and wrecks, NOAA charts, bathymetry, reef habitat, sea temperature, wind, weather radar with an 18 hour forecast for the continental US, and the bite score map), live cam playback, offline map areas, encrypted backup and sync, and GPX export. Pro is $12.99 a month or $99 a year, each with a 7 day free trial, or $149 once with no trial. Those are US prices, and other countries differ.
No. It's a model estimate, shown with a confidence percentage, and it appears in the Spearfishing, Scuba and Freediving modes. Free and Pro users see the same number. After a dive you can rate the visibility you actually had, from 0 to 5, and the server rounds that report's position to a cell about 5 km across without keeping the exact point.
Not for most of it. Conditions, the map, the Fish tab, trip recording and your spots all work without one. You need a free account for Safety Watch, to report a shark sighting, to share a reef or wreck or pin it to your spots, and to buy Pro. Encrypted backup and sync also needs an account.
Trip recording does. It records your GPS track on the phone with no signal, as long as the app is open on screen. Pro offline areas save the bathymetry and the reefs and wrecks for a box you pick. Forecasts and conditions need a connection, so check them before you head out.
Wind, waves, swell, sea temperature, tide and current work worldwide. NOAA tide predictions, National Weather Service warnings and the NOAA chart layer are US only, and the reef and wreck map is dense in US waters and sparse elsewhere.
Yes. Spots live on your device, there's no limit on how many you save, and there are no public or community spot maps. If you turn on Pro backup and sync, your spots and trips are encrypted on your phone before they upload.
Check your spot before you load the car.
Today's conditions, safety tools and trip recording are free. Pro adds the 8 day forecast, the Pro map layers, cam playback and offline areas for $12.99 a month or $99 a year, or $149 once.