NOVELTY - The apparatus (2) has a cylindrical housing (4) in which an electronic detection unit (10), a fuel reservoir (6) and an arrangement of micro-fuel cells (8) are arranged. The arrangement of the micro-fuel cells is connected to the detection unit. A water source i.e. separate water tank (14), connected with the reservoir is arranged in the housing. The water tank comprises a releasable closure (18). The water source is formed as a water inlet opening (12) that is integrated into the housing. The detection unit comprises a storage unit, which stores detected positions in certain intervals.    USE - Portable emergency apparatus for detecting a person or an object in an underwater surface associated with the apparatus by emitting an emergency signal in form of an alerting signal on standardized emergency frequencies.    ADVANTAGE - The micro-fuel cells have smaller dimensions in ranges of micrometer, thus making the arrangement to be a fuel cell stack with a three-dimensional matrix array, and hence achieving enhanced compactness for the apparatus by arranging the fuel cells in a small space. The arrangement of the fuel cells is placed inside the housing, so that wear and damage to the fuel cells can be avoided. The material of the housing can be selected in order to ensure sufficient strength and shock allowances and withstand intense mechanical loads, thus making the apparatus to have increased service life while avoiding maintenance requirements and reducing related losses to operational readiness. The apparatus exhibits improved reliability and safety.    DETAILED DESCRIPTION - The fuel reservoir is designed as a solid hydrogen reservoir, a liquid reservoir and an organic hydrogen carrier reservoir. The releasable closure is designed as a seal and a mechanical closure element. The reservoir is made of an ignoble metal selected from a group of periodic systems or hydride sources in form of metal hydride.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic plan view of a portable emergency apparatus.    Portable emergency apparatus (2)    Cylindrical housing (4)    Fuel reservoir (6)    Micro-fuel cells (8)    Electronic detection unit (10)    Water inlet opening (12)    Separate water tank (14)    Releasable closure (18)