I found this game to be frustrating. Normally, I like puzzle games. I enjoy playing Tetris and even recently tried out Lumines to much success. Downstream Panic! though just made me annoyed once I got a few levels into the game and it became too complex and required constant attention.
The basic idea is that you have to save fish. Sounds easy, right? If you thought that, you would be wrong. The fish start in a bubble in the sky and once the level starts the fish begin to fall. On their way down the screen the fish collide with various land areas and continue falling until they reach the limited safe zone or are killed by an enemy. While the fish, and the water with them, travel downward you, as the player, must save as many as you can by blasting holes, using plants to block them or using switches to limit the flow of water.
Using a style and level design similar to the Worms series of games, missiles can be used blast holes to carve up the landscape. The other common tool, the plants, act on the fish and water blocking them on the limited land masses and can be used to guide the fish. Both the fish and especially the water have their own physics too and act out accordingly when presented with a wall or hole that suddenly impedes their path.
Standing in your way to success are various enemies. Early levels have just the large sharks that line the bottom of the screen and surround the safe zone. Later levels have smaller sharks that become active once the fish and their water come into contact with them. The same water that can be used to hold fish in one area before hitting a switch and letting them go, can also trap the fish with a small, hungry shark.
For the more causal puzzle game fans, this game will rank a rent. For those hardcore puzzle game fans, those willing to lose over and over again to find that special, single solution to each level, well, this game is for you. Expect to see simple levels that elicit smiles as fish fall from a single source in the sky early on and later levels require constant attention to guide the fish around enemies and control the right amount of flow of water to allow the minimum amount of fish to reach safety.