Family: Perciformes: Thunniform Swimming

Class: Actinopterygii
Order: Perciformes
Family: Scombridae

Scombridae is the family of the mackerels, tunas, and bonitos.
Scombrids have two dorsal fins, each of which can be depressed into grooves in the back, and a series of finlets between the rear dorsal fin and anal fin and the tail. The base of the tail is slender, and the caudal fin strongly divided. Primarily swift predators of open seas; some of the smaller species strain zooplankton through their gill rakers.

Example of a Scombridae. This one's a mackerel.

Mode of locomotion is Thunniform:

Most fishes move by generating an undulating wave along their bodies along their bodies that pushes water backwards but thunniform swimmers isolate this movement to
The side-to-side amplitude of the wave is relatively large along the whole body, and it increases toward the tail.
Each wave is generated by contractions of the eel's muscles in a few anterior segments on one side of the spine while the muscles on the other side of the spine relax and slightly stretched. The resulting bending of the body towards the side of the body that is contracted passes backwards as the wave of muscle contraction moves towards the posterior. While this is happening the anterior muscles, which have been contracted relax, their partners on the other side of the spine contract and the eel bends in the opposite direction. The fish produces thrust using this oscillation.

wiggle wiggle

Interestingly eels can swim backwards as well as forwards using this method of locomotion. This method of locomotion works for the eels lifestyle for a few reasons, eels can move quickly to capture prey and being long and thin mean they can hide in cracks and small spaces before rushing out on prey. Being able to swim backwards can be used as an efficient method of evading capture from predators.

Amount of body used for propulsion with anguilliform
In trigger fish the anal and dorsal fins are slightly inclined towards each other to a net forward thrust is produced. This balistiform method allows the fish to manage complex manoeuvres such as backing up, hovering and sharp turns using their pectoral fins. The caudal fins are sometimes used to provide a short burst of (relative) speed.

Order Tetraodontiformes
Family Diodontidae

The family Diodontidae contains the Porcupine fish and the Burrfishes
Porcupine fish has the ability when threatened to inflate its body by swallowing water (or air) and become round like a ball. The sharp spines extend radially outwards, making it much more difficult to swallow and present an additional deterrent for would-be predators; this defence seems to be insurmountable for all but most determined predator. Some porcupine fishes also carry the extremely deadly poison tetrodotoxin in their skin and/or intestines. So it's apparently not wise to mess with the porcupine fish.

Mode of locomotion is diodontiform:
Diodontiform method of swimming involves localised anguilliform undulation of the moderately broad pectoral fins.

Like the Balistidae family the porcupine fish may also use its caudal fin for short bursts of speed. Lift generated with pectoral