A faked death, also called a pseudocide, is a case in which an individual leaves evidence to suggest that they are dead to mislead others. This is done for a variety of reasons, such as to fraudulently collect insurance money or to avoid capture by law enforcement for some other crime.
People who fake their own deaths sometimes do so by pretend drownings, because it provides a plausible reason for the absence of a body.
There are several how-to books on the subject of faking one's death, including How to Disappear Completely and Never Be Found.