In strict Jainism, seaweed is generally not considered allowed.

Reason:

• It is an aquatic living substance and may contain or involve many small जीवs.
• Harvesting it can cause violence to numerous water beings, which goes against ahimsa.
• For this reason, most Jains who follow a strict diet avoid seaweed and seaweed-based foods.

So, the safe Jain answer is: avoid seaweed.