Without spoiling anything major, in the novels, Meng Hao encounters the old boatman and the little girl who is a sort of spirit of the little lake. She wants to become a sea one day. MH promises her that one day he will help her do so when he has the power. The old boatman then offers him a cup of alcohol which then causes him to power up.
I really like the side plot with Guyiding Tri-Rain (the girl). As with all xianxia/wuxia to manhua adaptations, I strongly suggest you read the novel first. Especially for ISSTH. It's one of the best ones out there and it's completely translated.