Hi Graham ,
The snake headed Boat are called "Chundan Vallam" .
Here is a Link with all the details of the Boat , crew and its tradition during Aranmula Boat Race.
Please visit : http://en.wikipedia.org/wiki/Chundan_Vallam
Hope you have received all the details you required.
Thank you for visiting.
(N.B) : The Ideal Way shoot this Boat Race is to Hire a Private Boat in Advance and shoot from that Boat.
i put up my two Beach Umbrellas and 2 Plastic chairs on the Opposite side of the Main Venue. It soon became too crowded and i had no room to move my Location. i can tell you that even 400mm is Less, need a 600mm to 800mm to reach Opposite Bank. i am planning to Hire a Boat and shoot this event from an entire different angle this year in Aug - Sep 2104.