This particular species is considered short in comparison to the rest of the family; adult specimens of H. semperi that have been caught have a total length (including tail) of 50 to 70 cm (20 to 28 in).

Like its close relatives, its nostrils are located almost dorsally, with valves that prevent water from entering its nasal (and oral) cavities when the snake is submerged.

The only freshwater sea snake in the country, it lives the entirety of its life within the confines of the lake, feeding and breeding in its slightly acidic waters.

It is this unique aspect of the lake's formation and history that led to the evolution of several once-saltwater species, including H. semperi.

As with "true" sea snakes, H. semperi is piscivorous, feeding primarily on the numerous fish species that are known to dwell in Taal Lake's murky waters.