dark scarab beetle (?) with shiny blue underside

dark scarab beetle (?) with shiny blue underside

Observation - dark scarab beetle (?) with shiny blue underside - UK and Ireland. Description: Found this poor thing while doing pond dipping, right way up motionless on the surface. Thought it was completely dead but even 20 mins later is still trying to move...but turning itself to its back and I am not too hopeful!

Found this poor thing while doing pond dipping, right way up motionless on the surface. Thought it was completely dead but even 20 mins later is still trying to move...but turning itself to its back and I am not too hopeful!