We stayed on the beach late and dinghyed in at near dark. I drive the dinghy and my buddy normally secures it to the cleat. Later on I am at the back of the boat and realize the dinghy is gone. I yell the dinghy is gone, he comes back and is saying we need to go find that dinghy. We look and we can just make it out in the distance floating off. There isn't much wind so we both dive in to swim to it. It is pitch black behind us and we can just barely make out the grey dinghy pretty far off. I quickly recognize this is a bad idea and turn to swim back to the boat and there's a slight current making it difficult to swim to the boat so i yell to throw us noodles. We get back to the boat and i go to the front to assess our mooring ball and decide I'm not comfortable leaving our ball at night, I'm not sure if we'll be able to find it again at dark. While I'm assessing this my son who is 16, and a lifeguard, dives in after the dinghy, I yell NO! I know he will not be able to get it and he'll not be able to safely swim back. We now can't see my son, I know he will soon be tiring and I know I have to go get him. I run down to turn on the navigation lights and search light, start the engines then run up to take a mental note where the ball is relative to boats next to me and lights on land. We release the lines and we search for him by the sound of his voice and some small flashlights. We retrieve him and we then go grab the dinghy. I now head to hopefully find the ball in darkness. My buddy is pointing me off to the right but I know exactly where I'm headed and with my group with flashlights up front I pull right up to the ball and we tie off. Son back in the boat, dinghy retrieved, back safe on the ball. I had to make quick decisive moves, directing my crew, while keeping calm. Once back on boat I sat on the back and broke down. I relived that scenario over in my head many times since then. Still makes me a bit emotional thinking about it. Day 9, 2 crazy situations, one in the morning, one at night. Every other day was all good. I checked the lines every time after that. I always double checked the lines for our mooring before, but I made sure that dinghy line was good thereafter. Before we went to bed each night we put the dinghy on the transom and lift out of the water, but we normally left it off because we liked to watch the tarpon come swim our boat attracted to the underwater lighting.