Fish is a versatile mutant that uses his high mobility and ammo income to outrun and outgun enemies. Because of his ability to dodge enemy fire or quickly hide behind cover and his significantly increased ammo income, Fish can be recommended for beginners.
With water boost, Fish is propelled at rolling speed for as long as the active button is held down. Unlike the normal roll, Fish is able to change direction and stop at any time. This makes Fish highly evasive though not invincible and somewhat hard to control; as such water boost is mainly best for running away from hazards or back towards a safer area. (or coming near hazards to hit them)
Weapons don't use ammo to fire for 7 seconds after entering into a new level, including the rad cost of Ultra Weapons.
While Fish can be a great starting character for the ammo bonus, his roll takes time to master. Note that the roll does not stop when hitting walls and instead bounces outward but the distance is short and it can be used rapidly. The roll is mostly used to dodge enemy projectiles and grab distant pickups before they disappear or just to move faster and hide behind cover. Be careful when using the roll to dodge projectiles, however, as you can roll into more bullets.