Sawfish
Sawfish are primarily found in coastal marine and estuarine brackish waters, but they are euryhaline (can adapt to various salinities) and also found in freshwater. The largetooth sawfish, alternatively called the freshwater sawfish, has the greatest affinity for freshwater. For example, it has been reported as far as up the Amazon River and in Lake Nicaragua, and its young spend the first years of their life in freshwater. In contrast, the smalltooth, green and dwarf sawfish typically avoid pure freshwater, but may occasionally move far up rivers, especially during periods when there is an increased salinity. There are reports of narrow sawfish seen far upriver, but these need confirmation and may involve misidentifications of other species of sawfish.
Snailfish
In October 2008, a UK-Japan team discovered a shoal of "Pseudoliparis amblystomopsis" snailfish at a depth of approximately in the Japan Trench. These were, at the time, the deepest living fish ever recorded on film. The record was surpassed by a snailfish that was filmed at a depth of in December 2014 in the Mariana Trench, and extended in May 2017 when another was filmed at a depth of in the Mariana Trench. The species in these deepest records remain undescribed, but it has been referred to as the "ethereal snailfish". The deepest-living described species is "Pseudoliparis swirei", also of the Mariana Trench, which has been recorded to . In general, snailfish (notably genera "Notoliparis" and "Pseudoliparis") are the most common and dominant fish family in the hadal zone. There are indications that the larvae of at least some hadal snailfish species spend time in open water at relatively shallow depths, less than .