My reply was 3000 years of evolution is seldom wrong.
The river has pools of smooth water between dams that have been made from loose rocks. The loose rocks have channels or sluices through them – usually but not always there are two channels – one for upstream traffic – one for downstream.
It is entirely a man made river flow but the environment itself is stunningly gorgeous.
The advantage is that there are long sections of deeper water and little current for good travelling This is punctuated by the sluices of faster moving water for both a fun ride downstream and abbreviated struggles against the current. The sluices are made of large rocks … so the boat scrapes and bounces.
Some of the sluices have wooden beams across so that the boat is pulled up over those rather than the sharper rocks. Making it easier for the boatmen. But many of the sluices the boatmen are acrobatic and are jumping from inside the boat to outside and pushing mightily with their legs against the rocks to defeat the strong current. Very athletic!
If you zoom down in this google map you can see the whitewater areas between the calmer pools. Each drop is about a metre or a bit more.
The tourists (us) sit in the boats and relax and the boatmen push or even drag the boats up over some of the shallow sections.
The boats are super smart. They are narrow and long for good paddling. The upswept ends ensure that a collision with a rock will never do any significant damage as the boat will slide up on the rock rather than impact.
OK … wooden boats are my thing .. but you can easily see how the shape has derived from simple fabricated boats consisting of maybe 3 or 5 planks with a flat bottom section for stability, seating and large surface contact on any rock. But now all the boats are heavy fibreglass rovings for a good working life. The timber gunwales are easily replaced … probably yearly.
I did catch some photos of a wooden one from some distance away. I was wondering about whether there were wooden ones still and where to find them but on my second last day a wooden one passed by the riverfront house I was in.
Some of the other boats have been fitted with briggs and stratton type aircooled motors and act as tow boats or go about their individual business. Small powerplant, but low drag hull and they really move along – maybe 7 to 9 knots.
The rear curvature of the canoe is not ideal for the faster speeds under motor so small planing plates are added underwater so the water sees a flat bottom at the stern of the boat. If this is not done the boat will be much slower and also will motor with its bow high in the air.
The fee (2012) is Pesos1370 (about $33 each) and the boatmen might angle for a tip from the start of the trip but will be very helpful and chatty to give you a nice time. But hey … you are rich … right!?
(thanks Lita, Maida, Ria, Lani, Fiona and that huge extended family of yours! A real feeling of Filipino kindness and hospitality!).