Post your own challenge to your fellow researchers!
If they exist the only advantage of developing movement could be avoiding predators rather than trying to reach the light. Also I watched a documental about a type of photobacteria that swims up to get light and then goes to the deeps when reproducing to avoid genetic damage from the sun radiation. NatGeo has lied to me a couple times at least, so I don't totally trust this information.
PEACE & LOVE,