Results confirmed the detrimental effect of water on biological material and explored it with respect to variables chosen to account for the variability of fluids, conditions, and substrates arising from criminal activities. The results allow for a true comparison between three types of body fluids exposed to immersion in sea and river water with nine checkpoints in time over 3 months. Results show the expected rates of success for DNA profiling when the samples, covering a range of fluids and substrates, have been submitted to water immersion of given duration. The ability to recover DNA STR profiles using this multiplex kit is significantly affected by water exposure, depending strongly on the nature of the body fluid involved, the nature of the water, and the duration of immersion. This work provides guidance to the DNA analyst in assessing and prioritizing items collected from underwater crime scenes to maximize the expectation of obtaining relevant DNA profiles. A case strategy can then be agreed upon, concerning the samples offering the best opportunity to result in investigative information. Data were collected during a field experiment where stains, made of saliva, sperm, and blood, were left on various objects mimicking as closely as possible items of evidence found in casework; each sample was genotyped and the recovery rate of alleles was studied as a function of the immersion duration, the type of water, the type of substrate, and the nature of the stain. Tables, figures, and references