All ship classes suffer a severe accuracy and firepower penalty against PT Imp Packs. Secondary batteries on Cruisers and Battleships are good way to deal with them.
Before Nov20 JST evening, the original mechanism that provided Destroyers with the appropriate accuracy and firepower bonus against PT Imp Packs was not properly implemented. It has since been reported as fixed. But some players claim a decreased opening air strike accuracy and decreased seaplane effectiveness against them after the fix.
Type 3 Shells, Seaplanes, Skilled Lookout, 12cm 30-tube Rocket Launcher, & Bombers are speculated to be effective as well, but this claim may require further testing.
Now it is reported that replacing one or two red gun on cruisers with yellow gun work pretty well against them. Destroyers can use high-angled green guns.
It is assumed that they have extremely high evasion so anything that improves your hit rate will be very beneficial such as--but not limited to: CTF combined fleet, sparkling morale, fit guns (fit & overweight), surface RADAR and other Akashi improved★ equips.
They are most likely a reference to the Patrol Torpedo boats deployed by United States Navy during the World War II.
Currently the only non-boss abyssal ships with voice lines.