The act of hovering is not a form of rest for fish with swim bladders.

[gwand]

For fish, hovering uses double the energy of resting, study finds

Fish make hanging motionless in the water column look effortless, and scientists had long assumed that this meant that it was a type of rest. Now, a new study reveals that fish use nearly twice as much energy when hovering in place compared to resting.

phys.org