His goal isn't to milk her dry--and by now the description seems quite contrary to her actual state--but to achieve a level of contentedness he'd been struggling to obtain for the last few hours. Once he gets out the last drops of her orgasm, he finally lets her go. The tentacles in and around her loosen their grip, and they slowly, gently fall from her body as Boxer slowly tumbles from the ramp and into the depth of his tank, quickly falling into a blissful slumber at the bottom of it.

It means two things: one, Boxer will now have a really efficient healing session now that he's hopped up on meds and rubbed out his anxieties, and two, Sybil now has ample time to experiment and play around with her newfound...buoyancy.