Alma referred to his being snatched from the darkest abyss. His beholding the "marvelous light of God" seemed to happen rapidly and very dramatically. That happens to us some of the time, but not always. In a talk titled "The Spirit of Revelation," Elder Bednar compared the receiving of spiritual light to two physical experiences with light:
The first experience occurred as we entered a dark room and turned on a light switch. Remember how in an instant a bright flood of illumination filled the room and caused the darkness to disappear.
This was comparable to Alma’s initial experience. In contrast, Elder Bednar’s second example entails a more gradual perception of light:
The second experience took place as we watched night turn into morning. Do you recall the slow and almost imperceptible increase in light on the horizon? In contrast to turning on a light in a dark room, the light from the rising sun did not immediately burst forth. Rather, gradually and steadily the intensity of the light increased, and the darkness of night was replaced by the radiance of morning. Eventually, the sun did dawn over the skyline. But the visual evidence of the sun’s impending arrival was apparent hours before the sun actually appeared over the horizon. This experience was characterized by subtle and gradual discernment of light (Elder Bednar "The Spirit of Revelation").
Most of us have the "sunrise" experience of conversion, which slowly brings us into the light. Note, though, that Alma, who had the instant light did not let his conversion stop at that first bright moment. He continued to seek the light.
David A. Bednar, "The Spirit of Revelation," General Conference Address, April 2011, online at churchofjesuschrist.org.