Stuck...on first mission

[Mariner8]

I am something of a veteran of Jane's 688(I) HUnter Killer simulation. The Los Angeles sub in Sub Command is virtually identical to the earlier sim so I really had no problems getting to grips with Sub Command. I might point out that I bought these games in the Naval Combat triple pack and have read thoroughly the 688 manual, although I haven't read or printed out the Sub Command manual as I didn't want to waste all that ink only to find that the manual didn't teach me anything new (I've had that annoying experience in the past)

However as embarrassed as I am to admit it, I can't complete the first mission Super Escort, where you have to escort a super tanker through a straight and sink enemy subs. I've deployed towed array done radar sweeps listened for ESM etc. But the problem is this; I can't seem to get above 17 knots even with flank speed ordered. Why is this? Also, the sea is very shallow and I have sometimes run aground. The tanker you escort travels at around 11 knots meaning that even at 17 knots I can't get much ahead of it to clear the area. I've tried slowing down to 4 knots to listen passively, but have only heard enemy torpdeoes so far I've tried active sonar, with both single and continous ping, but in the busy straight contacts have been inconclusive.

Afetr about 10 attempts all my missions have followed the pattern of this; I manage to get a little bit ahead westwards of the tanker, slow down to listen out for subs, but only hear neutral shipping or enemy torpedoes by which time either I have been sunk or the tanker has.

So can anyone explain how this mission is supposed to be won.?I found it quite frustrating that the grizzled combat veteran I was in 688 (or that's how I like to imagine myself ) could be so easily beat in a sim so similar. Appreciate any help!