Abstract: A compact battery-powered flashlight adapted for underwater use which includes a casing, an illumination unit, a sealant device and a connection device. The casing is hollow and substantially oval in cross section while having a closed rear end and a head receiving forward end. The head receiving forward end of the casing has a hollow outwardly protruding cylindrical neck. The casing further is adapted to receive at least two parallel adjacent rows of batteries with at least one battery per row. The casing neck is axially aligned with one of the rows of received batteries. The illumination unit is mounted upon the neck and generates light upon electrical connection to the batteries. The sealant device is disposed between the illumination unit and the neck for providing a watertight seal therebetween. The connection device is used to electrically connect the illumination device to the batteries received within the casing.