At Cleethorpes beyond the swimming pool was the boating lake where we used to play as children. It featured rowing boats that could be hired by the hour, and had two small tree-covered islands in the middle. We would hire a boat and row it around the lake until our time was up. If we overstayed, a man would come alongside the edge with a loudhailer shouting the immortal "Come in number 15, your time is up." It was actually quite hard work for small children since the boats were heavy, and so were the oars. We would usually put ashore at one or both of the islands at some stage, tying the boat carefully to some overhanging branches to prevent it drifting away and leaving us marooned.
There was a legendary monster in the lake. The water was not deep, and one could see to the bottom. Mostly there was only mud, reeds and slime to see, together with odd items of discarded litter, but there were fish in the lake, and there was the monster. It was a giant grey eel, or at least it seemed that way to us. Sometimes we'd see it gliding along the bottom as we looked over the side. Compared to the small fish it seemed huge, and we imagined that if we stepped into the water it might bite us. It added a frisson of adventure and excitement to every boating trip as we looked out for it.