In a saucepan over high heat, combine the black-eyed peas. water, salt, and pepper. Bring to a boil, then reduce the heat to medium. Cover and cook until the peas are fork-tender, 25-30 minutes. Drain and cool under running cold water. Drain again and set aside.

In a frying pan over medium heat, fry the bacon, stirring often, until crispy and golden brown, about 10 minutes. Using a slotted spoon, transfer the bacon to paper towels to drain.

Add the red onion, garlic, and corn kernels to the hot drippings in the pan and cook over medium heat until tender, about 5 minutes. Stir in the vinegar and the sugar. Continue cooking until the liquid has reduced by one-third, 3-5 minutes. Using a slotted spoon, transfer the contents of the frying pan to a large mixing bowl; add the cooked black-eyed peas.

Add chopped tomatoes to the mixing bowl. Halve the cucumber lengthwise and then peel, seed, and finely dice. Add to the black-eyed peas and season with salt and pepper. Toss to mix well. Add the lime juice and the olive oil to the pan and swirl over medium heat until heated through, about 1 minute. Stir in the cilantro and ground coriander.

Divide the watercress among individual plates. Divide the black-eyed pea mixture evenly among the plates. Spoon the hot dressing over the salad, again dividing evenly. Garnish with the green onions and bacon and serve at once.