Under the Blue Horizon

Under the Blue Horizon is an idle aquarium builder that refuses to take over your screen. Your tank lives anywhere on the desktop, in dead space beside your work or along the bottom edge, growing fish while you do literally anything else. Pavdup and Chyopa released it on Steam in August 2024, and it belongs to the growing family of bottom-of-the-screen companions alongside Rusty's Retirement and Tiny Pasture, with a pastel underwater coat of paint all its own.

What the loop feels like

You feed shrimp to small fish, the fish grow, and they drop byproducts you scoop into Aqua, the currency. That's Under the Blue Horizon.

You spend Aqua on helpers, crawfish and jellyfish that automate the harvesting, until the tank mostly runs itself. That's Under the Blue Horizon.

An hour later you glance down and a dolphin has appeared, because you had been quietly satisfying its unlock quota all along. That's Under the Blue Horizon, and the glance is the entire interaction model: it is a game you visit, not one you sit down with.

The species ladder and the friend economy

The spine of progression is the species tree: around 42 fish, each unlocked by raising a quota of its predecessor, from small fry up to dolphins and whales. Wrapped around it is the helper economy. Crawfish and jellyfish optimize collection, while the special friends each unlock a whole management tab, a clam tab for passive income, a coral tab whose placement spawns themed fish, and a music tab run by DJ Octo, who supplies the integrated lofi playlist. The game is candid that the soundtrack and window management (always-on-top display, monitor switching, zoom, repositioning) are features, not garnish: it is as much ambient tool as game.

The prestige twist is the most creative system in it. Once you unlock all walls and space upgrades, starting a fresh run does not just reset numbers, it changes the environment entirely, with altered water textures, sea foam and clouds, plus a mermaid bonus for completionists. Reset loops rarely come with a reason to want to see them again.

Where it stumbles

The Steam verdict sits in mixed territory, and the criticisms are consistent. Depth is the main one: once the fish roster and helper set are unlocked, the novelty thins out, and the community ranks Rusty's Retirement as the mechanically deeper standard of the genre. Window behavior draws smaller complaints, with quirks around layering and clicking when active apps overlap the tank. And if you want active progression, the waiting-heavy loop is simply not built for you.

Playing it today

Live on Steam for Windows and macOS at a budget price, from publisher DEVDUP. Best enjoyed in genuinely dead screen space rather than as a main event.

The verdict

Aesthetically it matches anything in its genre, and as fire-and-forget ambience it succeeds completely. As an incremental, it is a light appetizer rather than a meal, and it knows that. If the genre hooks you, Chillquarium is the full-window take on the same appeal.