A great underwater clamp to use is a titanium clamp for saltwater. Even the screw is titanium, no ZERO rusting like the stainless steel. Even the plastic deteriorate and snap over time. I've had them installed for years and they still look brand new! They're called Titan Clamps, 100% titanium. They will last a lifetime but they're around $8 each when I bought them. But it's the only clamp I'd trust underwater.
Nice. Sit up, the only problem is the older I get the better a remote sump looks. It sux trying to climb back behind drain lines to hook up or unhook a pump.