Here's my take on that. It is Murphy's law that when you realize the problem, the boat ramp is full, a line waiting to get put in, and your trailer is blocked from being moving.
So, disclaimer-Don't do this in cold water. But, if water conditions permit......
Put on a life jacket. Skipping this step while you are already having a heart attack causes funerals.
Grab the plug tightly, or have someone hand it to you.
Jump in the water with the engine off
Put the plug in from in the water
Stop the situation from getting worse!!!!!
If your bilge works, you may have the problem solved in mere minutes. Don't go to Davy Jones locker waiting for the ramp to open up. I guess you could gently beach on the sand if plugging in the water isn't an option.