Large Lake in the middle of 17.16 (3pp)
Canal on the border between 14.14 and 15.13 (1pp)
River from the middle of the border between 18.19 and 19.18, through the borders between 17.18 and 18.18, 18.18 and 19.17, 17.17 and 18.18, 18.17 and 18.18, 17.17 and 18.17, and to the lake in 17.16 (9pp)
River from the lake in 17.16 to the borders between 16.16 and 16.17, 16.16 and 15.16, 15.16 and 15.15 (4pp)
River from the lake in 17.16 to the borders between 16.16 and 17.15, 16.15 and 17.15 (3pp)
1pp remaining.
Do Note that a Canal is meant to just be a very thick river. You're not following the elevation rules for the canal on the beach bridge. However, I will allow it, as it is not impossible to think that a natural waterway might connect the two oceans.
Only 8 points for the split river in the mountains around 18.18, as it only connects to that many hexes. However, the river going west from the lake, costs 5pp, since it touches 5 hexes, The last river is the same, 4pp, because you need to include the point from 17.16. Otherwise, you are breaking the elevation rule again. but since the waterway connects to the ones in the mountains, I will accept it.
20-3-1-8-5-4=0
Medium Lake in the middle of 14.04 (2pp)
Medium lake at 15.02 (2 PP)
River from the center of the mountain lake at 14.04, waterfall half way to 15.03,
canal leading into 16.03 (12 PP)
^Connections into the sea at 15.03-16.04 and 16.03-17.02 (2 PP)
1 PP remains
The first river would cost 2pp, then the 2nd river leading out from that would cost another 2pp, for a total of 4. Then the waterfall costs 10.
19-2-2-2-2-10=1
waterfall on 15.09 leading out to 16.10
Going to assume you mean river here and THEN waterfall?
Large lake in the middle of 4.17
River from 14.04, to 14.03, to 14.02 and finally into the ocean.
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