Some sharks mind low saline levels less than others. There are river sharks like the Ganges shark, or Bull sharks that even flourish in both worlds. The Pondicherry shark (Carcharhinus hemiodon) seems to tolerate fresh water, too. Named in 1839 by German biologists after the Indian territory Puducherry (former Pondicherry) where it was documented first, it can be found in rivers and coastal waters in the Indo-Pacific around India, Indonesia and New Guinea. It is an extremely rare species of requiem sharks that not much is known about. It seems to grow not much longer than 3.3 ft -1 m- (although the German wikipedia page claims a maximal length of 5 to 6.6 ft – 1.5 to 2 m) and is ovoviviparous (like all other requiem sharks).

Given that most known specimens were captured before 1900, there are rarely pictures of living Pondicherry sharks. Since their habitat has been heavily and unregulated fished, the IUCN regarded this species in 2003 as critically endangered and possibly extinct. However, in 2016 it was spotted in rivers in Sri Lanka, where it has been found infrequently over the least 30 years.

Sources: here, here and here