Send announcements of S.W.I.M. Fitness Challenge (lose weight, Super Bowl Sunday to start of Illinois state meet on April 19, ILMSA being the host LMSC) to Weight Watchers, Jenny Craig, Biggest Loser, and Crossfit.
One doesn't have to know how to swim or even get wet to participate in the S.W.I.M. Fitness Challenge; one need only be a member of USMS.
As a long-term outreach effort, working with Weight Watchers or Jenny Craig to do an annual promotion of benefits of swimming, maybe with assistance on finding a pool or coach for interested nonswimming adults, combined with a dedicated goal of weight loss should prompt a nice bulge in membership.