The earlier comment about doing a first dive in daylight is very important, it make the site familiar and helps with night navigation.
Night diving requires closer buddy pairing.
Also, with night dives, I use 3 lights. Two lights to see by and a tank marker light (either red or green. I find green shows up better if water is not as clear). If your buddy's light fails you know where they are even before they get out their back up light. ALso if the water is very clear, and the moon is out, and you are shallow, by previous agreement you may shut off both lights for a few minutes. Very cool to look up at a moon through the water. The tank marker lights help to quickly keep track of where each other is.
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Does the spring have a "cave" that is easy to avoid during day that one of you might accidentally enter at night?
Night diving requires closer buddy pairing.
Also, with night dives, I use 3 lights. Two lights to see by and a tank marker light (either red or green. I find green shows up better if water is not as clear). If your buddy's light fails you know where they are even before they get out their back up light. ALso if the water is very clear, and the moon is out, and you are shallow, by previous agreement you may shut off both lights for a few minutes. Very cool to look up at a moon through the water. The tank marker lights help to quickly keep track of where each other is.
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Does the spring have a "cave" that is easy to avoid during day that one of you might accidentally enter at night?