I Bug with Rubber legs is a really effective Argentiean Sea Trout pattern.  Good for dropping under cut-banks on the far side of the rive ras its small compact shape helps it sink quickly.   As with many Argentinean Sea Trout Flies the more at odds they appear with natural imitations the more effective they seem to be!  Go prepared with the widest selction of flies possible and be prepared to experiment size and weight and colour throughout the day to get the best results.