I spent last week at Hocking Hills State Park in Ohio. It is a beautiful gorge with several waterfalls. I took almost 500 photos including some with an IR filter. These all used a 35mm 1.8 prime lens on a tripod. They were 30-45 second exposures.
Cameras auto exposure are often way off for IR work. What camera were you using?
Obviously it's not a converted one, but IR response from standard models varies wildly, My old K100d has enough response to handhold in good conditions whilst many others hardly see any IR.Many modern models will block IR so effectively that they'll just record images from the trace visual light leaking through the filter. I can (just) see bright items through my '850nm' filter, and standard 720nm filters let through more still.
FWIW at shady gorge is not likely to have a great deal of IR available, making your job even more difficult.