Abstract: A method, system and computer program product, the method comprising: obtaining a first multiplicity of images from an overhead capture device overlooking a body of water; detecting a swimmer in some of the images, wherein the swimmer is outside the body of water or separated from other swimmers; determining two descriptors of the person, based on the images, the first descriptor related to a portion of the swimmer outside the water, the second related to a portion inside the water, the descriptors determined upon visual characteristics extracted from the images; obtaining a second multiplicity of images from the device; and tracking the swimmer in the second multiplicity of images, said tracking comprises detecting the swimmer using either descriptor, said detecting the swimmer is performed with respect to an image from the second multiplicity of images in which the swimmer is partially occluded by other swimmers or adjacent to other swimmers.

Abstract: A method, system and computer program product, the method comprising: obtaining a multiplicity of images taken by one or more overhead capture devices overlooking a body of water having a surface; detecting a person depicted in at least some images from the multiplicity of images; determining for images in the images, whether the image depicts the person in substantially vertical position in the at least some images said determining performed upon one or more characteristics extracted from each image; and subject to determining that the person is not in substantially vertical position in the at least some images, taking an action.