Many strainers appear rather harmless. They can be trees with no branches underneath with water flowing under them. Whats underneath is the scary stuff. A short branch protruding can catch your shoulder strap on your PFD. What if there is an inconvenient rock sticking up under the water? Strainers are great trash collectors. Could a shopping cart be hidden below - maybe? Strainers have claimed the lives of a number of boaters over the years. You can do a search on the AW Accident Database via this link: AW Accident DB Search. I know there are many more incidents than have been reported in this database.