Working Boats in Vietnam, on the Mekong Delta from what google translate tells me,
I presume its some sort of flash gate, but there must be several openings in the bridge
The unladen wooden boats are fast, and there are several videos of this location
https://www.youtube.com/watch?v=xH-VXhoIXH0
Tug sinks about 5 mins in
https://www.youtube.com/watch?v=vwjQSQgzqSk
found the location
https://www.google.co.uk/maps/place/Đại+Phúc,+Càng+Long+District,+Tra+Vinh,+Vietnam/@9.9959483,106.3065841,445m/data=!3m1!1e3!4m5!3m4!1s0x31a0111b9d50c553:0xaedf35035df353da!8m2!3d9.9804029!4d106.293406
and purpose - its a tidal barrage to stop salt water coming too far up river and affecting crops
springy