There is a close analogy between electric current and hydraulic current if you consider the electric voltage (potential difference) as a height (altitude difference), and if you neglect all possible extraneous effects. The current goes down the potential as the water goes down the altitude. This is a graphic illustration of the current/voltage convention:
In this simulation, electric charges are assumed to be all positive. Therefore the electric current flows from the positive (+) terminal to the negative one (-), which is the same direction as the charges. In electronics, negatively charged electrons flow from the negative (-) terminal to the positive (+) terminal of the supply, but conventional current always flowing from the (+) to the (-).
Click on the tap and the switch.