Octopus uses an attack that can cause Slow and it is armored, so Tidus, Wakka and Rikku may have a hard time damaging it unless one of them has Armor Break. However, it is very weak against lightning, so Rikku's Electro and Lightning Marbles should be able to easily defeat it.
The one and only visit to its location is perhaps early for characters to have the Bribe skill, but those who do have it can obtain 20 Healing Water for 4,500 gil each, where other fiends "charge" 5,600 or more.
Although Octopus has, like most enemies, a list of potential equipment drop abilities, it is set to roll 0 random abilities and thus almost always drops blank equipment. The only exception is when dropping weapons for Auron or Kimahri; as with most enemies' drops, these will always have Piercing, but nothing else.