Tonight a band of lizardfolk was towing a large raft (some 30-feet square raft) over shallow swamp waters. Some 4~5 feet deep. Since the raft had some several key townsfolk tied up on it and was on its way to be sacrificed to some hideous demi-human deity, the wizard decided to cast web below the raft.
His rationale was that the web would anchor between the raft and the swamp floor, trapping some of the lizardfolk but also stopping the raft from moving.
He was underwater, had water breathing on, and could see underneath the raft, so targeting was not an issue.
Would the web anchor (prevent movement of) the raft?