potomac levels are currently ok. The rise doesn't happen immediately, anyway. Hit it at low tide. there are plenty of spots near chain bridge you don't need to really wade, so long as you don't mind scrambling over some rocks. Alternatively, rent a boat from fletchers and head up river. When the flow is strong youll have a much easier time in a canoe than in a raft, provided your comfortable anchoring a canoe etc. in strong current.