because you think you're good, you know. >> we usually keep, like, three cases. three cases of gallon waters. >> okay. >> which is probably like 12 gallons at the most. >> oh, that's terrible, guys. that's terrible, okay? >> fear is a very immediate motivator, and i think it's therefore an especially powerful tool in marketing for good and for bad. >> reporter: adam alter is a professor of marketing at the nyu sterns school of business. he says entrepreneurs like darren and dave use fear in a very direct way to market their products. >> what i would like you to do is make a plan and then work your plan. >> one of the big keys is if people are feeling fearful, that you also give them a tool or tools to deal with that fear. and you give them a sense of control. >> i really equate it back to insurance. our demographic is people who want to be able to be comfortable and survive if there's an emergency. >> so they actually manage the fear, overcome it. even though the chance of something bad happening is small, we want to know that it's something we don't have to worry