Most synthesizer preset bass sounds are absolutely useless for DUB music. Try to program one yourself instead:

Start with a square or triangle wave and filter away almost all of the harmonics using a low pass filter. You will end up with something close to a sine wave.
Program the amplifier envelope so that you get a sharp attack and a long sustain phase. A short peak at the beginning of the curve gives you a nice "finger-pluck"
Alterningly you could start with a sampled note from a real bass which will result in a more natural sound.
Off course use the EQ on your mixing desk to boost the low frequencies. (Caution: Filter away frequencies below ~20 Hz. These will only stress the amps and speakers of the system and not do much for the sound!)
(2) Here’s a collection of rumors on how distorted Drum & Bass / Jungle bass sounds are made:

"what I’ve heard optical (king of basslines) does for alot of his neurosis is take a 909 bass drum, stretch it out, and filter the piss out of it in a morpheus or compatible piece with z plane filters.

Of course old analogue stuff is great. the Jupiter is still used alot (doms nyc,ny), junos, moogs. but another filter over that is helpful so you don’t sound too 'electrode', or too 'hooverey'." "Something I've been trying lately is synthesizing a raw 60-90hz sine wave, about 5 seconds long, and putting a tiny bit of decay on it. I'll copy and paste it in a sample editor about 8 or 16 times, and then start running slow, long effects on the entire mess...phasers, flangers, distortion, echo, anything. I'll keep adjusting the bass with eq and maxxbass to preserve the frequencies, and eventually come out with bizarre, droney basslines. Throw some filters and an amplitude envelope on top of it, modulate the filters and envelope with a Midi CC, and the blines just squawk and screech. The trick in the mix is to keep the low frequencies strong, keep the mid-range squawk strong, and find a frequency where the mids won't fuck with your drums...and I still haven't personally nailed the mix..."
Start with a low pass filtered square wave. (one single note)
Adjust the pulse width of the square wave somewhere off center.

Apply distortion and reverb.

Take a sample of this and play it with a lot of portamento. Sampling is needed because this way the delay is cut at the end of each note.