I think Patrick is right, this is Spoon worm (Phylum: Echiura). We noticed similar type of organisms in Tropical Godavari Estuary during post-monsoon period of 2010.
If the specimen is avail with you, i may suggest you two peoples in Chennai. Dr.K.G.Sivaramakrishnan, working @ MCC Chennai as Emirates Professor another Dr.K.Selvakumar working @ zoology department of Anna University as PDF, they may be help in this regard of identification