I love that invasion force
. Playing DiD and wanting to last the whole war gives me plenty of opportunity to take on that force.
Assuming you're using RFB2 and RSRD, I'm usually in the spot you're in right now... those three escorts seem to spot me and hone in quickly. I wonder if they're not simply screening for the rest of the force, though... and I just happened to be in their way.
Submerge soon enough, hope they don't notice that hole in the water, and they'll wander off.
I'll either wait for night, or simply slink in past the circle of escorts as quietly as I can. I'll wander a bit inside the circle, firing my fish off, sinking as much as I can... empty both bow and stern tubes. Depending on the escort situation and the weather (usually 5 m/s winds at that point), I might even stick around to reload tubes and get another shot off.
Staying at 'scope depth seems to help... but don't get too brave. There's been a few times where I swore that escort wasn't bearing down on me 'cause he knew I was there... and he sank me as a result.