A sponge swims by squirting water out through a tube
It will drink from the main body of water that it swims in. And yes, it does need clean water. That's a thing that most living creatures need.
There is no osmotic difference. This happens more with freshwater vertebrates than marine creatures.
swims in the open water
it swims.
it has a lower desnity than the water
a gold fish swims in a fish tank or the sea.It Swims I The Water And Eats Fish Food
it swims in deep water
it is a bird that swims on water such as a swan or duck.
swims,silly!
Medusae
No, you imbecile - it swims.