# Hydrostate vs Underline

The clearest difference is ads: Underline at none against Hydrostate's shown. Underline also leads on update cadence (every 2 days vs every 2 weeks). Hydrostate's advantage is iOS requirement (15.0 vs 17.0). On price, in-app purchases and device support there is nothing between them.

Both are free to download. Hydrostate sells 12 one-off in-app purchases and Underline sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

Hydrostate ships an update every 2 weeks, Underline every 2 days. The most recent releases landed on October 25, 2026 and October 31, 2026 respectively.

## The numbers

| Metric | Hydrostate | Underline |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.3 (12 ratings)](https://appshunter.io/ios/app/hydrostate-water-network-3d/id6755589355/reviews)** | — |
| Number of ratings | **12** | — |
| Positive reviews | 0.0% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | Yes | **No** |
| Update frequency | Every 2 weeks | **Every 2 days** |
| Monetization | Free with in-app purchases | — |
| Size | 350 MB | 393 MB |
| Requires iOS | **15.0** | 17.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 9+ | 4+ |
| Developer | [AAM GAMES LTD](https://appshunter.io/developer/1745519754) | [Harry Attenborough](https://appshunter.io/developer/1896491884) |

## What reviewers say

### Hydrostate

[App page](https://appshunter.io/ios/app/hydrostate-water-network-3d/id6755589355)

Build and manage a city's water system by connecting pipes and optimizing flow. Solve challenging puzzles, upgrade your network, and expand your water empire in a vibrant 3D environment. Enjoy relaxing yet engaging gameplay as you ensure every building receives water.

**Highlights:** Build and connect water pipes, Manage water flow and pressure, Solve logic and planning puzzles, Upgrade and expand city water network, Experience beautiful 3D environments, Relaxing and engaging gameplay

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (12)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Get 7 Water Tanks | $0.99 | one-time |
| Cash 300k | $0.99 | one-time |
| Cash 300K | $0.99 | one-time |
| 75 Gems | $0.99 | one-time |
| Get 16 Water Tanks | $1.99 | one-time |
| Auto Cash Collector | $1.99 | one-time |
| Remove ads discount | $1.99 | one-time |
| Cash 1M | $2.99 | one-time |
| Remove Pop up ads | $2.99 | one-time |
| 1M Cash | $2.99 | one-time |
| 250 Gems | $2.99 | one-time |
| Starter Pack | $4.99 | one-time |


### Underline

[App page](https://appshunter.io/ios/app/underline-metro-builder/id6805291888)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Unlock Everything | $7.99 | one-time |


## Frequently asked questions

### Is Hydrostate free?

Hydrostate is free to download, with in-app purchases available.

### Is Underline free?

Underline is free to download, with in-app purchases available.

### Do Hydrostate or Underline have ads?

Hydrostate shows ads; Underline does not.

### Which is updated more often, Hydrostate or Underline?

Hydrostate ships an update every 2 weeks, and Underline every 2 days. Most recently, Hydrostate was updated on October 25, 2026 and Underline on October 31, 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.*