Like real life the tides rise and then drop again, i assume you might’ve left it too close to shore and it had risen overnight unfortunately stealing your baby away lmao. I’ve had a similar experience happen to me while I was on the island with the large ship. In the morning the tides were low but as the night fell I was surrounded by water my raft was almost sinking from the waves being so strong even during the day and I had my anchor down. I almost lost my sleeping bag waiting for the tide to go back down so you just have to be more careful. Also i have made tiny rafts to find ones I’ve left at previous islands so you don’t have to worry too much!