How can cartilagenous fishes float in water inspite of not having swim bladder ?

Question

How can cartilagenous fishes float in water inspite of not having swim bladder ?

Answer 1

1) Their density is very close to that of water, because they store large amount of lipids called squalene

2) The shark's body is positively cambered, like an aerofoil, so when the shark is swimming the water flowing over it generates lift.

Answer 2

The specific gravity of cartilaginous fishes is maintained very close to that of the ambient sea water by a process of fluid balance similar to osmosis. Thus fish such as sharks usually have a slightly higher overall SG than the water in which they swim and would slowly sink if they stopped moving. In fact bony fish also maintain this slight negative buoyancy but the swim bladder allows them to  react more rapidly to changes in water density.