Unidentified swimming insect

Unidentified swimming insect

Observation - Unidentified swimming insect - UK and Ireland. Description: There are two insects on the first picture which to my untrained eye appear to be different species.

There are two insects on the first picture which to my untrained eye appear to be different species. Or possibly different.... The upper insect I think is a Greater Water Boatman. The lower, I don't know. The second image is a blow up of the lower insect. Of course, I could be wrong on both counts. Help, please!