What water bug am I? Students version

1. This bug lives in clean flowing rivers under rocks
it has pincers and lots of legs.
What am I ?

2.In am up to one Inch long 
If I am a adult I will have no mouth
I am found in flowing clean water 
What am I ???????????

3.I get eaten by Aquatic Beetles

I poo with my mouth 

I breath through my skin

What am I ?

4.they are red and black

they are part orf the spider family
they are carnivorous
What am I ?

5.Adult is known turns in too a bee fly 
It was a breathing tail 
Grows 7cm long
What am I ?

6.Lives in still or slow flowing water.
Body has 13 segments.
Less than 10mm long.
What am I ?

7.I am a completely flat insect

We breath threw our skin

And we live in water

What am I ?