Additionally, Ecco, being a mammal, must surface periodically for air, or else find an air vent. If the "air meter" runs out, Ecco loses health rapidly, which represents drowning. His health is measured by a separate meter (above the air meter); it is depleted by enemies or when his air meter runs out, and it is recharged by eating fish, "singing" to clams, or, later in the game, singing to special statues or glyphs. Ecco's song can be optionally upgraded at two points in the game: one upgrade allows Ecco's song to be used in combination with a charge as a long-range weapon, and the other temporarily disorients sharks and makes minor enemies freeze temporarily. Touching any enemy by any means other than an attack causes Ecco to sustain damage. The enemies range from seahorses to giant octopods.