# Subsurface vs Poseidon Reef

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.

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.

## The numbers

| Metric | Subsurface | Poseidon Reef |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.5 (48 ratings)](https://appshunter.io/ios/app/subsurface-mobile/id1093217161/reviews)** | [3.0 (2 ratings)](https://appshunter.io/ios/app/poseidon-reef/id1581432645/reviews) |
| Number of ratings | **48** | 2 |
| Positive reviews | **63.3% of reviews** | 0.0% of reviews |
| In-app purchases | No | No |
| Ads | **No** | Yes |
| Update frequency | Every 2 months | **Every 5 weeks** |
| Monetization | **Free** | Ad-supported |
| Size | 52 MB | 58 MB |
| Requires iOS | 17 | **12.1** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod, Mac** |
| Age rating | 4+ | 4+ |
| Developer | [Dirk Hohndel](https://appshunter.io/developer/1093217160) | [Poseidon Diving Systems AB](https://appshunter.io/developer/567839779) |

## What reviewers say

### Subsurface

[App page](https://appshunter.io/ios/app/subsurface-mobile/id1093217161)

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.

**Highlights:** Mobile dive log management, Edit dive data, Download from Bluetooth LE dive computers, Optional cloud synchronization, Open-source and free

**In-app purchases:** none


### Poseidon Reef

[App page](https://appshunter.io/ios/app/poseidon-reef/id1581432645)

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.

**Highlights:** 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

**In-app purchases:** none


## Frequently asked questions

### Is Subsurface free?

Subsurface is free to download, with no in-app purchases.

### Is Poseidon Reef free?

Poseidon Reef is free to download, with no in-app purchases.

### Which has better reviews, Subsurface or Poseidon Reef?

Subsurface is rated higher. Subsurface averages 4.5 out of 5 from 48 ratings, while Poseidon Reef averages 3.0 from 2 ratings.

### Do Subsurface or Poseidon Reef have ads?

Poseidon Reef shows ads; Subsurface does not.

### Which is updated more often, Subsurface or Poseidon Reef?

Subsurface ships an update every 2 months, and Poseidon Reef every 5 weeks. Most recently, Subsurface was updated on October 6, 2026 and Poseidon Reef on September 30, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*