New robots  have been created to monitor the state of water

Scientists from the University of the West of England (UWE) have created a moving robot that uses the energy obtained from photosynthesis. They called it MARS - marimo-activated rover system. Its name explains the principle of the robot's movement - a marimo-activated all-terrain system The robot is a small, 3D-printed exoskeleton about the size of a baseball, inside which is a ball of algae and a mechanism to check the water condition.
The exoskeleton protects the robot from strong water currents, and the algae ensure its movement. These algae, known as marimo, are usually found in fresh water and have the appearance of a dense green ball. As a result of photosynthesis, the oxygen bubbles produced by the algae hit the walls of the exoskeleton and rotate the ball, due to which the robot is able to move along the bottom of the river or lake.
Despite the fact that the speed of MARS depends on the level of sunlight, it can be said that it is not a fast device. As a result of the experiments, it was found that the robot moves at a speed of about 9 cm/hour, like, for example, a snail. Despite its slowness, it nevertheless serves as a viable and practically effective means of dynamic environmental control. Such robots have a number of advantages: they are much more affordable from an economic point of view, and they are also biodegradable.
An article on the development was published in the Journal of Biological Engineering.