My favourite film too. Wow - beauty image! Timing was spot on to have the water fall at the end of the exposure. The rocks and steel complement the soft water perfectly.
I have a box of APX100 5"x4" left with about 5 sheets, 20 odd rolls 120 and some 35mm, I'll never buy again as I prefer to use same film across all formats. Tmax 50 is just as good but a stop slower, never understood why they call it Tmax100 - on a more serious note I find that the two films are very similar, it's just the Kodak needs to be used at 50 ISO to get the same tonality - they do say that in their literature.
Have some AP25 and APX25 in reserve 120 & 35mm, for special occasions, ie when not enough 5"x4" darkslides with me !