Tarpon, Sharks and Billfish are all typically captured off a boat, and toa large extend the boat does a big part of the battling. But even if you was to put a tarpon or similar in a still lake and copare it pound for pound it wouldn't fight as hard for as long.
You have to understand that the Mekongs power comes from its design, a huge tail, and even bigger anal fin which combine together to displace so much water in a single sweep of the tail that you just cannot fight back!