In Jainism, the concept of the lifespan (āyu) of various types of beings, including those residing in different elements, is described in detail. According to Jain scriptures, water-bodied beings (aprakāya jīva) have a specific maximum lifespan.

Water-bodied beings (aprakāya jīva) are said to have a lifespan (āyu) of one antarmuhūrta, which is slightly less than 48 minutes.

A prahar is a traditional Indian unit of time equal to 3 hours (one-eighth of a day).

So, the lifespan of water-bodied beings is not one prahar (3 hours), but one antarmuhūrta (less than 48 minutes) according to Jain texts such as Tattvartha Sutra and commentaries on Jain cosmology.

References:

• Tattvartha Sutra (5.21)
• Dravyasangraha, Verse 24
• Jainendra Siddhant Kosh

If you have more questions about Jain cosmology or concepts, feel free to ask!