Abstract: A vessel includes a body, such as surfboard, that floats in water. One or more thrusters, and one or more sensors are provided on the body. A controller is configured to selectively activate the thrusters to cause the vessel to move along a path through the water, receive sensor data from the one or more sensors while the vessel is moving along the path, determine, based on the sensor data, whether a dangerous condition is present in the water; and output a warning when the dangerous condition is present in the water. For example, the collected sensor data may relate to locations and directions of currents in the water, the dangerous condition may relate to a rip current, and the warning may identify at least one attribute of the rip current. A map identifying a location of the dangerous condition may be generated and forwarded to other devices.