Spearfishers only want to know one thing before heading out: Spearo turned "go in the water or not" into red, yellow and green lights across 85 countries

Spearo is a sea-conditions forecast app for spearfishers and freedivers. It hit Google Play at the end of July, and by Nov it had 6 installs 37,838, with 1,651 added in the last week. Over the past 2026 years, there have been at least a dozen small products doing underwater visibility forecasts, and their predictions aren't very accurate. Spearo has the most installs, thanks to reach: 85 countries, 9 languages, and one web page per coastal city. This piece covers what it is, where the traffic comes from, where the money comes from, and whether you should squeeze into this category.

"Nowhere else has this, it's just too optimistic"

In Aug 8, a user named Kyle from South Africa left a review on Google Play for Spearo, and 8 people later marked it helpful: "Every local spot has an estimate, which is great. Nothing else has this. But the model is a bit too optimistic. It says visibility is 3 to 4 meters, and in reality it's only 1 to 2 meters." He also wants the app to explain which factors drove each verdict, since in South Africa sardine runs change fish behavior a lot.

Over two months later, on Oct 15, someone on the US App Store gave it one star, titled "Garbage AI slop": "You have to pay $43 for a subscription as soon as you open it, and it's not accurate. I bet they built it in a day with Claude."

The two reviews describe two sides of the same product: the people who want it really do want it, and it really is rough. The store page's opening paragraph describes what this audience has to do before heading out: "Most of us check three or four apps before getting in the water: one for wind, one for swell, one for tides. You drive to the coast and the water is still murky." Spearo gives a single verdict: green means there are windows today and it tells you which hours; yellow means marginal; red means don't go today, and it tells you the next good day. It also gives underwater visibility in meters.

How big it is, and how it grew

From mid-August to late September, it added over 20k installs in six weeks, right in the late-summer diving season in the Mediterranean and US. After October it slowed to 1,200 to 1,700 per week. On Play it has 235 ratings averaging 4.2 stars, and it shipped 9 versions in 8 days, so it updates often.

On the charts it has stayed near the bottom. On Google Play Sports Free, its best showing was #35 in the Philippines (10-29), and then it dropped off the charts. The only one still listed is #95 in Australia, 11-06, and it's climbing. As winter arrives in the north and summer in the south, its traffic is shifting with the hemispheres.

The iOS version launched on Jul 10, with the developer shown as an individual, "Diana Dryn". It didn't go in Sports. It went in the Weather category and charted in Weather Top Grossing in many countries: #9 in Greece, #9 in Cyprus, #11 in Lebanon, #19 in Portugal, #23 in Brazil, and #67 in the US (App Store, around 11-06). Top Grossing charts in small-country Weather categories have low bars, so a few subscriptions a day can get you on them.

Where users come from

One web page per city. The site spearo.app is in 9 languages (English, Portuguese, Russian, Spanish, Italian, Greek, French, Turkish, Croatian), and it batch-generates pages by coastline: "spearfishing forecast for [place]", "tides and water temperature in [place]", "spots and seabed maps for [place]", "spearfishing regulations in [country]". The US has 367 spots, Italy 113, France 95, Greece 83, Spain 73, Portugal 42. The homepage says it covers 85 countries and 2,600 cities. In search engines you can find its Russian page for Malta, Portuguese page for Funchal, and Turkish and Croatian tide pages. Searches like "[place] tides, water temperature" have far more volume than "[place] spearfishing". Every page carries Play and App Store download buttons and QR codes, so visitors are sent straight to the store.

One store title per country. It's the same iOS app, but the titles change by country: "Pesca Sub e Marés" (spearfishing and tides) in Brazil, "Pesca Submarina y Olas" (spearfishing and waves) in Spain, "Meteo Mare e Pesca Sub" (sea weather and spearfishing) in Italy, and "Chasse Sous-Marine" in France. Locals searching "tides" or "sea conditions" can find it, and being in the less competitive Weather category lets it chart in dozens of countries, which brings some free exposure.

Meta ads (probably running, scale unclear). A Facebook page called "Spearo" was created 2026 years ago, has 1,200 followers, and since Oct 4 has posted short videos with copy along the lines of "Drove an hour to the coast and can't see a thing? Check your stretch of coastline before you head out", linking to the website, which says "Free, no sign-up needed". The third-party site Peekly shows 94 Meta ads running (unverified). Its Play ranking in cheap-traffic countries like the Philippines, Indonesia and Malaysia in Sports, and attribution parameters on the website's download buttons, all match paid acquisition.

Not found: No official TikTok account, and nobody makes content for it there. Nobody mentioned it on X in the past 90 days. No press coverage, and no Product Hunt launch. On Reddit's r/Spearfishing there are several self-promo posts from "I built a visibility forecast tool", but it can't be confirmed which, if any, is from Spearo.

Where the money comes from

Subscriptions. The Play version is free to start: no ads, no sign-up, and the first few days of forecasts are free. A weekly forecast, saving more spots, and following more locations need Pro. The annual Pro plan has a 7-day trial, and there's a pricier Ultra tier, with in-app prices of $5.99 to $69.99. The iOS version pushes a subscription as soon as you open it, which is why the US iOS version has only 9 ratings at 2.7 stars. On Sep 21, a one-star US review said: "The Android version is free and does much more. The Apple version is an outrageously expensive subscription." The latest version also adds invites: friends invited without a card get 14 days of Pro free, and inviting three people earns you a month.

The two platforms do two jobs: Play drives installs and builds ratings, and iOS collects the money. Peekly estimates about $5,000 a month on iOS and about 5,000 downloads (third-party estimate, unverified). Its ability to chart in Top Grossing across several countries' Weather categories shows people are paying. The scale is probably a few thousand dollars a month, no more (inference).

Who it's competing with

This is a typical 2026-era category: one person plus AI, built in a few weeks. The visibility data comes from the same few sources for everyone: the EU's Copernicus satellite water clarity data, the US NWS and NDBC buoys, and Open-Meteo sea conditions (the data sources its own site lists are these same ones, all free). Similar products you can find:

Nothing in scale comes close. Rivals are mostly locked to one country or one coastline; it launched across dozens of countries and many languages from day one. On accuracy it has no edge: Kyle calls it too optimistic, iOS reviews call it inaccurate, and its site claims "proprietary models and buoy calibration" that outsiders can't verify.

Why this one took off

• The audience is small and scattered worldwide. Spearfishers are spread across the Mediterranean, the Americas, Southeast Asia, and Australia/NZ, with only a handful in each country. A product for one country can't get enough volume, so it covers 85 countries and picks up a little long-tail search in each, which adds up to first place in its category.
• One verdict, not a pile of charts. The pain point is "I drove an hour and the water is murky", and it answers the go/no-go question directly.
• Picked the right category and keywords. On iOS it sits in the Weather category with titles packed with "tides" and "sea conditions". Small-country charts have low entry barriers, and charting brings organic installs.
• Seasonal tailwind. The six weeks when it grew fast coincided with the late-summer diving season in the Northern Hemisphere.

If it were you

One-line verdict: Competing head-on in spearfishing forecasts isn't worth it. A dozen-plus people are building at once, it already covers dozens of countries, and the whole category likely earns a few thousand dollars a month in subscriptions. The thing worth taking away is its playbook.

Who it fits: Indie developers who can build programmatic pages and pull public weather and ocean data, who have a hobby audience that's a small group in each country served only by local tools, and who are part of that community themselves, e.g. a niche like shore fishing, kayak fishing, snorkeling, or kitesurfing.

Who it doesn't fit: Anyone wanting to build yet another spearfishing or dive-visibility forecast (the data sources are open to everyone, it's hard to differentiate on forecast accuracy, and it already holds the multi-country, multi-language position); anyone hoping to make big money in this category (the audience is too small, low ceiling); anyone without a cold-start channel who can only wait for organic store installs.

How to do it: If you insist on staying in this category, do what it did poorly: accuracy. Divers want real local measurements, so have divers report actual visibility on the day, calibrate by coastline, and show people why a verdict was reached. Start by saturating one coastline it covers thinly and where you live, such as a stretch of coast in South Africa or Southeast Asia, in the local language. If you switch categories, copy its structure: public data APIs, one verdict, one page per city, multilingual, free on Play to drive installs, subscriptions on iOS.

How to get users: Build programmatic pages that also target big keywords (tides, water temperature, regulations), with download buttons on the page. On iOS, pick a less competitive category and localize titles per country. For cold start, go to the audience's Facebook groups and Reddit communities, where people ask every day "what app do you use to check sea conditions?"

Deadline: There's no window in this category worth rushing for. If you're building for southern-hemisphere coastlines, December to February is peak season, so launch before December.

What would show you're reading it wrong: ① In the southern-hemisphere summer (December to February) its weekly growth climbs back above 3,000, showing the October slowdown was seasonal and the category pool is bigger than it looks; ② it discloses revenue or gets acquired, with monthly revenue far above a few thousand dollars; ③ a major player like Windy or Surfline adds visibility and a go/no-go verdict, in which case the whole category, including this app, needs to be recalculated.

Data and sources

• Installs and ratings: Google Play (10-29 to 11-06); early installs from AppBrain (08-15) and apppage.net (09-28) snapshots.
• Charts: Google Play Sports Top Free by country (10-29, 11-06); App Store Weather chart by country (around 11-06).
• Store page copy, Play reviews and developer replies: Google Play store page (accessed 11-06); iOS reviews: App Store US storefront (08-19, 09-21, 10-15).
• Website and data sources: spearo.app (accessed 11-06); spot counts per country from the website's country pages.
• Ads: Facebook "Spearo" page; active ad count from Peekly, unverified.
• Revenue: third-party estimate from Peekly, unverified.
• Competitors: their websites, store pages, AppBrain, TikTok.
• Where you see "estimated", "inferred" or "unverified", that's what it means.