Hello I guess the underwater ...

Hello I guess the underwater plants are Hydrilla, while I can also see few lilly plants with heart shaped leaves. They are indicators of unpolluted water and are good for the aquatic ecosystem. So let it be as it is. Thats why you have lots of fish, turtles and crocs in the lake. Any weed which over grows or dominates the particular ecosystem is bad. Weeds like duck weed (green small circular weed) and Water hyacinth are not good for any water body - but these are not there in your lake. However you should clean the lake of the plastic - by hand picking. Also grass is growing right in the middle of the lake which means there is lot of siltation. If possible silt from middle of the lake should be dredged out to deepen the lake a bit.