Submarius
The spearfishing app with a real water clarity forecast.
Every marine-weather app tells you the wind and the swell. That's table stakes. But spearfishing comes down to one thing: can I see the fish? Submarius answers that directly, with real water-clarity forecasts, tide and moon windows tuned for hunting, and a color-coded verdict you can read in one second.
Water clarity is the whole game.
In tropical reefs you're shooting at 25 meters of visibility and every fish is obvious. In turbid bays and estuaries you're lucky to see your own gun tip. Most apps ignore this entirely. A few show "wave height" and call it a proxy. That isn't how turbid water works.
Submarius starts from each spot's typical clarity for the time of year, built from in water measurements and satellite ocean color, then subtracts wave stirring judged against depth and bottom type, river and runoff plumes, and tide driven water movement. The result is an honest visibility estimate, shown as a low to high range with its sources, for every dive window.
When the forecast is wrong, the dialog tells you why: whether it's proxy data in a region we don't yet have direct measurements for, a recent storm that hasn't cleared, or a river that's dumping sediment. No black-box "you're good, go!", actual reasoning.
Tide + moon = hunting windows.
Slack tide for easy entries and clear water column. Spring tides for moving bait, neap tides for clarity. First and last quarter moons for predictable currents. Submarius computes every high and low, every phase, every window, and surfaces the 2–3 hour stretch each day with the highest verdict score.
This is the "best window" chip on the home dashboard. Plan your 5am alarm around the data, not around the weekend.
Your spots stay your spots.
Spearos guard GPS coordinates like combinations to a safe. Submarius was built with privacy as a day-one requirement, not a bolt-on:
- Public spots you share are fuzzed to ~1 km. Nobody can reverse-engineer your honey hole.
- Personal dive logs with precise coordinates never leave your device.
- Community vis reports submit only a coarsened (~1 km H3-tile) location alongside the report.
- Per-spot ACLs: private, friends-only, or public.
Privacy enforced structurally, not by policy.
Safety that stays free, forever.
OCEARCH tagged-shark alerts, community shark sightings, buddy GPS sharing, SOS, and breath hold blackout monitoring (planned) are permanently free. No Pro gate. No paywall. Some features shouldn't cost money, and gating them would be a PR disaster anyway.
What a verdict looks like.
Open the app and you get a number between 0 and 10, a word (PRIME, GOOD, FAIR, CHOPPY, ROUGH), and the one sentence that explains the driver: "Visibility estimate poor, turbid water likely, rising tide, 12 kts NE, 1.8m SE swell." Tap any factor for the full breakdown.
Every factor is tappable (wind, wave, swell, tide, moon, water temp, vis, best window), opening a drawer that explains what the number means, how heavily it's weighted for spearfishing, and a 24-hour forecast trend.
Common questions.
Yes, Submarius is built spearo-first. Our water-clarity forecast, tide/moon hunting windows, bottom-temperature layer, and post-dive visibility reports are all tuned for the question spearfishers actually ask: can I see the fish? The app broadens to cover diving, fishing, and boating, but spearfishing is the lens we design around.
The forecast starts from each spot's typical clarity for the time of year, built from in water measurements and satellite ocean color, then subtracts what changes day to day: wave stirring judged against depth and bottom type, river and runoff plumes, and tide driven water movement. Each estimate shows a low to high range and its data sources. Community post dive reports are collected to validate and improve the model.
Yes. Spot privacy is enforced structurally, not by policy. Your saved spots are never shared by default. When you submit post-dive clarity reports, coordinates are fuzzed to a ~1km H3 grid tile before leaving your device. We can't give away where you dive because we never see the precise location.
Yes. Current conditions, a 2 day forecast, basic bite score, and all safety features (shark alerts, buddy GPS, SOS) are permanently free, no signup required. Submarius Pro ($12.99 a month, $99 a year, or $149 once) unlocks the 8 day forecast, premium map overlays, offline maps, and advanced water clarity horizons.
Yes, anonymous-first by design. Open the app, check conditions, and go. Sign up only when you want to save spots across devices, post catches, or contribute visibility reports.
Ready to stop guessing?
Free forever for conditions, verdicts, and all safety features.