How to sink a "stationary" destroyer

Some info first. I'm using TMO 2.5, american campaign, S-18 sub.
So after a failed attempt at attacking an enemy convoy which resulted in game of hide and seek with few destroyers I decided to wait for a couple of hours at max depth until bastards get bored and leave me be. Waited until 21:00, ascended to periscope depth to check if coast is clear and saw lone stationary destroyer still waiting for me to surface.
Since he was stationary and unaware of my location I decided to sink him as he was perfect target (Or I thought so at least). Moved to his starboard at perfect 90% angle, about 1400 yards away and launched 3 torpedoes at him. All seemed well until he saw torpedoes on the way, started the engines and swiftly evaded them all (BTW. Those destroyers accelerate ridiculously fast. Like from 0kt to something that fells like 10kts in 4 or 5 seconds. I'm not claiming to be an expert on ships but that seems kinda silly)
So I loaded a save, got in the same position and tried again, this time launching the first torpedo directly at him, and next 3 torpedoes at 3,6 and 9% offset to the right so they catch him even if he starts engines and moves forward. This didn't work either. He managed to outrun all those too. Tried again. First torpedo directly at him, next 3 at 10,15 and 20% offset. He sees them so soon that he outruns even that 20% offset torpedo. I tried again at point blank range (500 yards) that didn't work either.
Anyway I'm out of ideas. Is there any tricks when trying to sink a destroyer? I tried all kind of things. Bastards just sees torpedoes and gets away. I am using Mk 10 torpedoes which are kinda slow to be honest but still...