Subsurface vs Poseidon Reef
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Subsurface
This application allows divers to manage their dive logs on their mobile devices. It supports editing dive data and downloading new information from compatible dive computers. Optional cloud synchronization is available for seamless data transfer with desktop versions.
- Mobile dive log management
- Edit dive data
- Download from Bluetooth LE dive computers
- Optional cloud synchronization
- Open-source and free
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Subsurface-mobile is an iOS dive log application based on Subsurface, the best free open source dive log application available on Windows, Mac and Linux. Subsurface-mobile allows you to access your dive log on your tablet or phone, edit the data and even download new dive information from many Bluetooth LE enabled dive computers. Using a free Subsurface Cloud Storage account you can synchronize your dive data with the Subsurface desktop application (while significantly increasing the usefulness, the cloud account is not required to use Subsurface-mobile). To get support from the developers, please use the in-app menu entry "Ask for support" Please check out the Subsurface-mobile user manual: https://subsurface-divelog.org/documentation/subsurface-mobile-v3-user-manual (also available from within the app) Subsurface-mobile is free and open source. No ads, no commercial anything. And it comes with free cloud storage (if you decide to use that - it's optional). Your data aren't used for anything, nothing gets monetized.
Poseidon Reef
This app helps divers log, plan, and analyze their dives. It offers detailed overviews, customizable dive logs, and advanced planning for various dive types. Connect your dive computer to manage data and firmware.
- Comprehensive dive logging
- Detailed dive planning
- Support for OC and CCR dives
- Unlimited tank support
- Decompression model selection
- Dive computer connectivity
- Cloud backup and firmware updates
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Dive into the deep with Reef, the ultimate tool for every diver regardless of experience, level, or dive style. Designed to enhance and prolong your passion for diving, Reef seamlessly extends your diving experience, both before and after the actual dive. With Reef in your pocket, you're always ready to explore. Dive Log > Get a comprehensive and detailed overview of all your dives. > Easily sort and filter to find specific dives. > Import and export dives effortlessly. > Personalize dives with custom details, photos, location and more. > Engage with your dives using the interactive chart functionality. > Visualize intricate data like tank pressures, pO2, loop temperature, etc.* > Choose the data points you want to see > Zoom in on portions of the dive you are interested in Planner > Keep track of all your upcoming dives with a comprehensive overview. > Sort, filter, and organize your dive plans. > Plan for a single dive or a series of dives. > Suitable for OC (Open Circuit) and CCR (Closed Circuit Rebreather) dives. > Supports an unlimited number of tanks. > Choose between DCAP and Buhlmann decompression models. > Bailout scenario > Configure gas content Device Manager > Connect your Poseidon M28 dive computer through WiFi > View details about connected submodules. > Download, store, and back up your dives in the cloud. > Access vital service information > Monitor total dive time > Stay updated with firmware information. *Only available with Poseidon M28 dive computer
Screenshots
Verdict
The clearest difference is review sentiment: Subsurface at 63% against Poseidon Reef's 0%. Subsurface also leads on rating (4.5 vs 3.0) and ads (none vs shown). Poseidon Reef's advantage is device support (4 vs 2) and iOS requirement (12.1 vs 17). On price, update cadence and in-app purchases there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
Subsurface holds the better App Store score, 4.5 against 3.0. That said, the two scores are not equally well evidenced: Subsurface has 48 ratings behind it against 2, so its average is the more settled of the two. Written reviews point the same way: 63% of Subsurface's written reviews are positive against 0% of Poseidon Reef's.
Subsurface ships an update every 2 months, Poseidon Reef every 5 weeks. The most recent releases landed on October 6, 2026 and September 30, 2026 respectively.
| Parameter | Subsurface | Poseidon Reef |
|---|---|---|
| Price | Free | Free |
| Rating | 4.5 (48 ratings) — better | 3.0 (2 ratings) |
| Positive reviews | 63.3% of reviews — better | 0.0% of reviews |
| Number of ratings | 48 — better | 2 |
| Update frequency | Every 2 months | Every 5 weeks — better |
| Ads | No — better | Yes |
| In-app purchases | No | No |
| Monetization | Free — better | Ad-supported |
| Devices | iPhone, iPad | iPhone, iPad, iPod, Mac — better |
| Requires iOS | 17 | 12.1 — better |
| Further details — not scored | ||
| Size | 52 MB | 58 MB |
| Age rating | 4+ | 4+ |
| Developer | Dirk Hohndel | Poseidon Diving Systems AB |
Customer experience
Subsurface
Poseidon Reef
In-app purchases
Subsurface
No in-app purchases
Poseidon Reef
No in-app purchases
Questions
Is Subsurface free?
Is Poseidon Reef free?
Which has better reviews, Subsurface or Poseidon Reef?
Do Subsurface or Poseidon Reef have ads?
Which is updated more often, Subsurface or Poseidon Reef?
Other comparisons
