As for anglers that claim to be able to locate springs on the bottom in 20 to 30 feet or more, I’m skeptical. I’m also skeptical of how much difference a spring at that depth is going to attract bass anyway, because water that deep is going to naturally be cooler. All you have to do to figure that out is take a dive off you’re buddy’s dock in summer and feel the difference about five feet down. I’ve heard guys say they use their electronics to find springs similarly to how you mark the thermocline. I’ve even heard about castable thermometers that are meant to provide pinpoint temperature differences in the abyss. I’m sure they work, but before you go down this path, be mindful that if you’re readings are going to be accurate, you’d have to cast the thermometer to a loads of similar depths outside of the area you believe is a spring. In short, it’s a ridiculous amount of work given that there is no decisive proof that bass even care about a deep spring. Find a shallow spring, and you’ve found some summer money.