What is this unusual creature swimming in Geylang River?

Stomper Raven witnessed an unusual creature swimming in Geylang River on Jan 5.

In the video he sent to Stomp, a black creature can be seen swimming in the muddy water.

Raven told Stomp, "First time I see something like this, it is very weird."

"It looks like a combination of a monitor lizard and a catfish," he added.

Do you know what is this creature?