A device for launching using compressed fluid, comprises: a projectile, a barrel having two ends, the projectile being positioned inside the barrel, a first of the two ends allowing the compressed fluid to enter the barrel, a second of the two ends allowing the projectile to leave, a reservoir of compressed fluid connected to the first of the two ends of the barrel. A connecting device comprises a first tape, able to make the transition from a configuration in which it is wound about an axis Z around a support to a configuration in which it is deployed along an axis X substantially perpendicular to the axis Z, the tape having an end fixed to the projectile, and wherein the support is fixed in the barrel.

A system for underwater hunting contains a plurality of components which allow for customization of the speargun based on the user's needs and the conditions where a user is hunting. By allowing rapid additions or removals of certain components, the invention allow the user to easily modify the firing characteristics of the speargun, and thus target a wider range of prey across a wider range of environmental conditions than those designs currently available in the prior art.