Safety features

Submarius treats safety features as ethically off-limits to the subscription business model. They are permanently free — not “free trial”, not “free-tier with limits”, not “free for one feature, paid for the rest”. Free.

The features

SOS

Press-and-hold the SOS button to fire an emergency signal. Submarius:

  1. Captures your current GPS position (with horizontal accuracy)
  2. Computes a Plus Code for the position — an open-standard, short, human-readable rescue location that works without street addresses
  3. Sends a message to your designated emergency contacts via push notification (if they have the app), SMS (fallback), and email
  4. Optionally fans out to the local Coast Guard / lifesaving service (where a published intake exists)

The rescue message includes your name, position, Plus Code, time of SOS, and (if known) your dive activity, last buddy position, and duration submerged.

Dive-buddy GPS sharing

Two divers can pair their phones for a single trip. While paired, each phone broadcasts its position to the other every 30 seconds via a real-time WebSocket. The pairing ends when either diver ends the trip or 12 hours pass, whichever comes first.

If a dive overruns expected duration, the surface buddy is alerted with the last-known position. If a phone goes offline, the other side sees the gap and the time of last contact.

Plus Code rescue location

Plus Codes (Open Location Code) are a Google-developed, open-source, short alphanumeric code that uniquely identifies any 14×14 m square on Earth. They’re more compact than lat/lon, easier to transcribe than DMS coordinates, and don’t require a street address.

Every Submarius position output (SOS, shared spots, catch logs) shows the Plus Code alongside the conventional coordinates. Coast Guard operators can decode them with publicly available tools.

Tagged-shark and crowd-sourced shark proximity

Covered separately in shark-alerts.md. Free, free, free.

Garmin inReach satellite SOS (planned)

For users with a Garmin inReach satellite communicator, Submarius will hand off the SOS to inReach for satellite delivery when cellular coverage is unavailable. This requires a Garmin partner integration and is on the roadmap, not yet shipped.

Why these are permanently free

Three reasons:

  1. They might save someone’s life. That’s not a feature to gate behind a $99/year subscription.
  2. Network effects. Buddy-GPS and crowd-sourced shark sightings get better the more users participate. A paywall on participation defeats the value.
  3. Trust. The brand promise of Submarius is that the app is honest about what it knows and what it doesn’t. Charging for an SOS button would be inconsistent with that promise.

The relevant entitlement middleware in the Submarius backend explicitly bypasses subscription checks for safety endpoints. This is permanent product policy, not a marketing free-trial period.

What safety features can’t do

Plain about the limits: