Confidence: It's likely to be this, but I can't be certain.
Notes: There are two possibilities, thoracicus and costae. The latter is a bulkier insect and is a species of upland pools. But the two can overlap. The view is ideal but this appears to be sufficiently wide across thorax to be a specimen of costae. The small insect is not a Microvelia; appears to be very early instar of a gerrid.