I managed to sink the Pride of Rotterdam, even when I not tried to sink it.
On the mission with Pride of Rotterdam from San Fransisco to Phi Phi Islands, when entering Phi Phi Islands the boat starts bumping and the damage goes to 90%. the result of this is that the boat sinks half in the water. Probably is this a bug, because the map says 23m depth, but the depthmeter says just above 7m.