What's up with the armoured Sampans and fishing boats?

[LukeFF]

My favorite example of how tough sampans could be in reality. From the 11th war patrol of the Pollack, 30 July 1944:

1222: Lat. 6d.-05'N; Long. 153d.-27.5'E - periscope sighted object which appeared to be a small sailboat.

1300: Closed object with 20mm. guns manned and 4" gun crew standing by in the conning tower. Determined object to be partly sunk and abandoned sampan of about 10 tons. Closed to 500 yards and fired 180 rounds of 20mm. and 60 rounds of 45 cal. (Thompson Sub Machine Gun) for indoctrination and training purposes. Backed clear, made another run and fired 5 rounds of 4"-50 cal. for same purpose. Results:~ One bird of Nipponese leanings definitely sunk; six more thoroughly scared; sampan now draws about two feet more water; 4" gun crew abashed because sampan was not blown out of the water.

Like tater said, some of these boats could be very tough. It's part of the reason why there was such a big push to get 40mm guns mounted, because they were far more effective than 20mm guns.