Like many fruit trees, your citrus tree is probably grafted…the stem or trunk is grafted to the root stock of another type of citrus. The water shoots are probably from the root stock and will not resemble or produced the fruit that the now-dead trunk. If you can determine that one of the shoots is growing from above the graft, prune the other shoots away and promote that one to replace the dead trunk. If they are all growing from below the graft, there is nothing that can be done. Water shoots should be trimmed away as soon as they appear so the roots continue to push nutrients and water through the graft rather than to have it diverted to the “suckers” or “water shoots”.