Mac Travis is a commercial diver.
His past is a bit of a mystery to most people, even the government folks with the power to do some substantial digging into his past. In one early adventure, his history was summed up by one investigator as "Name's Travis, Mac Travis. Been down there for years living off the land in typical Keys fashion. Strong minded guy. ... This guy is invisible. I've had a PI run down the basic stuff on him, and the numbers don't add up. He's pulling in a marginal income fishing and doing commercial dive work, but it doesn't add up. He pays his taxes, but has no bank accounts. He paid cash for his house and boat. That's probably five hundred thousand for the house and another two for the boat."
Travis has a secret history and he likes it that way. He also likes being left alone to live his quiet life, well, quietly. Unfortunately the world does not seem too obliging in that regard and when then it finds that when Travis is pushed, he tends to push back a bit harder.
Now making his home in the Florida Keys, Travis hails from Galveston, Texas, where he learned to work beneath the surface with his father, becoming not only a certified diver but also certified in underwater welding and concrete pouring and other useful trades, which is what eventually took him to Florida and the start of a new life.
Helping Travis in his work and his other extracurricular activities is Trufante, a 6'5" Cajun who also found his way down the thousand miles of coastline until he, too, lives and breaths the Key air. Trufante is an interesting character because he seems to find more ways to get Travis involved in things than Travis, a sane man, should allow.