I’ll introduce myself – waterfall pools explorers wanted

There are two similar to your description. And another that overlooks the reservoir, which might have an outside chance of being the one.
One of the two is situated along the access road between Shek Pik and Fan Lau. I haven’t been their in years due to it’s isolation even for Lantau residents. So I’m assuming the one you mean is the river at the junction of Tung Chung and Lantau roads (on Cheung Sha Beach).
You can access these popular falls either from the beach, the junction (path through the bushes) or the first bridge up Tung Chung Road and walk downstream.
Either way will get you and your indoor orientated girlfriend at the falls in around 10mins. Without breaking a sweat.
(quick point – Someone usually judges my route by how easily they can get their better half to the location, this location is the easiest. Although the pools themselves are good, for a bit more work you can get better)
As kids we used to jump off the large boulder at the NE (and called this location ‘Black Rock’ – until we discovered Ma On Shan’s huge black cliff-face).
We used to love this one for it’s convience to one of HK’s best beaches, (a party could easily split between the two all day), and great eating and drinking afterwards at either end of Chung Sha Beach. Many of my schoolfriends will never forget this location (wink,wink)
I don’t go there as often these days, no longer being a student means Lantau is restricted to weekends (uugghgh! – especially after we enjoyed mid-weeks there). And becoming a rock-pool affecianado means I know of better pools that are closer.

I’m waiting for the summer monsoon to end (which may have just arrived), then allow 1-2weeks for the water to clear.
Then I’m off.
I work freelance so I can get away mid-week occasionally. But will consider weekend hikes if the location isn’t a popular one.
My first will probably be a summer celebration at Siu Sai Wan Beach, Sai Kung. Great rockpool, great beach and a cafe nearby.
Then the next week I’ll be off to find a suspected pool in the upper reaches of the same river. There is a good isolated pool nearby with great jumps and black depths (even with mask) nearby so there will be no dissapointments. Although I’ll be coming at it from above and there may be no safe route down to the sure-thing. But it’ll only be a 15/20 min uphill back to the path.
And the week after that I want to try a hidden valley in Plover Cove with a faunal secret, to see the pothole jump again. There have been arguments about the sanity of doing it. But mainly to get acroos the pool which stopped us last time and see if the route from the top is easier.
As we get closer to the time, let us know if your still interested.

End of ‘summer monsoon’ will be in about 1 – 2 weeks hopefully. The summer monsoon is when we have 2 weeks of rain before the heat and humidity hit us full on. After this the rivers will need time to cleanse themselves clear again. again 1 – 2 more weeks.
Then the party ends in Oct/Nov with the ‘winter monsoon’ (cold winds)
Many of the country parks pools have a watershed of subtropical rainforest, and only halve in flow during the dry winter months and should still be good for swimming. Although most mountain drainage spurs will be dry.
For Lantau, I will discuss with friends about tackling the best one this summer and arrange a day.
The easiest one which is just OK is at the junction of Tung Chung and Cheung Sha roads at Cheung Sha beach. It’s a doddle and is great fun for the beach, and nearby pubs. My advice would be watch the weather forecast. I’m hoping this week will be a washout with flooding (summer monsoon).

HKwaterfalls closed down.
try this instead http://www.hkadventurer.com/ more info but you have to look harder for it.

I’m the same in terms of pace.
I could walk all day on the flat, but will stop when and where I like on the uphill. My excuse will usually be that it’s a good spot for wildlife. If I have to walk over a crest and down again to go upwards then you’ll hear me muttering under my breath.