Summarizing...
Tiny Animal (Aquatic, Swarm)
Hit Dice: 8d8+8 (44 hp)
Initiative: +2
Speed: Swim 40 ft. (8 squares)
Armor Class: 15 (+2 size, +2 Dex, +1 natural), touch 14, flat-footed 13
Base Attack/Grapple: +6/-
Attack: Swarm (2d6)
Full Attack: Swarm (2d6)
Space/Reach: 10 ft./0 ft.
Special Attacks: Distraction (DC 15)
Special Qualities: Half damage from slashing and piercing weapons, leaping glide, low-light vision, poison flesh, swarm traits
Saves: Fort +7, Ref +8, Will +3
Abilities: Str 4, Dex 15, Con 12, Int 1, Wis 12, Cha 2
Skills: Jump +18, Swim +5, plus 11 ranks
Feats: 3
Environment: Warm aquatic
Organization: Solitary or school (2-4 swarms)
Challenge Rating: 4
Treasure: None
Alignment: Always neutral
Advancement: None
Level Adjustment: -
Distraction (Ex): Any living creature vulnerable to the piranha swarm's damage that begins its turn with a flying fish swarm in its square is nauseated for 1 round; a DC 15 Fortitude save negates the effect. The save DC is Constitution-based.
Leaping Glide (Ex): A flying fish swarm may leap from the water and glide at a speed of 160 feet for up to 8 rounds. The swarm may reach a height equal to the result of its Jump check, then fly with clumsy manueverability. It may descend, but cannot ascend during this travel.
Poison Flesh (Ex): Ingested, Fort DC 15, 1d4 Con/1d4 Con. The save DC is Constitution-based.
Skills: A flying fish swarm has a +16 racial bonus on Jump checks, and uses its Dexterity modifier for Jump checks. A flying fish swarm has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.