i usually launch near fletchers cove for free or at Kenilworth. do note on the Potomac I think either DC fire for NPS will issue tickets if you don't have a PFD.

for clean water, i usually go to Beaverdam Reservoir. for shallow water Mason Neck State Park, but they close at sundown and they will lock u in the park.

always note the wind speed and direction before launching. it will save you

also Che-SuP-Peake offers entry paddle boarding sessions starting early spring