[codeduck]

5kg of plastic explosive will be more than enough to sink a ship.

[dogma1138]

No it won't, have you ever handled explosives?

[mjlee]

Wedge the watertight doors open, disable the salvage eductors and you can sink a ship by cracking a single sea water intake pipe open.

I'm on mobile so I can't provide a link, but look up the Argentinian Type 42 sunk in harbour or HMS Endurance for examples.