Hydro is perhaps the most unique map that ships with Team Fortress 2. The two teams are pitted against each other, each with a control point just outside their spawn under their control. The aim is for one team to capture the other team’s control point without losing their own. Relatively simple concept.
The twist is that there are many stages (8 in total), and not only are they chosen somewhat at random, but there is a transition of stages as one team or the other wins each stage. At the beginning of the map you are greeted with a strategic map which shows each team controlling 3 locations. Each stage is a contest between two of these locations, and the winner takes both. After the first stage, the now-taken location is put up against the other team’s forward-most location. If the team controlling 4 locations loses, it is back to the previous stage, but if the team with 2 locations loses, it becomes 5 vs 1 locations, and there is a final stage.
In the final stage, the team with only 1 location left must defend their final point, and the team controlling 5 locations must attack the final control point. The attacker’s control point is locked here, and if the defenders manage to hold off the attack, they reclaim the attackers’ location. However it is often difficult to defend, and if the attackers manage to capture the final control point, they win the map.
I have only included some general strategies and tips in this guide, due to the difficulty of covering vantage points given the massive combined area of all the stages of Hydro. I may come back and revise this decision at a later date, but for now enjoy what exists!