The female Rhydon's from Nintendo's Pokemon and this screenshot's taken from Valve's Garry's Mod.

She's just having fun pumping her belly up by storing up her Hydro Pump in it and this big mama's enjoying how giant, ocean-like and bouncy it is that she starts to dance and would welcome any of her adoptive kids to bounce up and down on her stomach like a trampoline, if they wish to do so.