The third antennal segment has several large bristles that are at least as long as the width of the segment and the first antennal segment length is much less than the combined length of the remaining segments. According to Epler's Identification Manual for the Aquatic and Semi-Aquatic Heteroptera of Florida 5.4, these are both characteristics of Rheumatobates. However, unlike Rheumatobates, the abdomen is not as long as the rest of the body. I certainly need an expert's help to identify this one.