We located C. bullosa in 2 other rivers near to the SungaiSeblak, I shall not reveal the names of the rivers here. Below are some photographs of the 1st river which looked slightly blackish. The C. bullosa found there were mainly in submersed form.
The 2nd river had both emersed and submersed C. bullosa, below are some photographs of it.
What surprised me was that C. ciliata could be found growing alongside C. bullosa in the same river.