While it makes great TV, the assassination that seems to be taking place in the Potomac explosion video seems unnecessarily complicated. First of all, those shells only weight about 55 pounds and there are few places to hide explosives. Possibly under the seat’s slide but it’d still be noticeable when the rower lifted the shell over his head or into the water. Some sculls have small ports in the bow and stern but unless the charge was incredibly light one could tell that the boat was off-balance fairly quickly.
Secondly, the security at the Potomac Boat Club is pretty good. The one street entrance has a combination locked door and the windows have metal grates. There are always people hanging around during the day and some no-goodnik messing with someone else’s boat would raise alarms. Rowers are a naturally suspicious people, the result of being mocked by football players in high school. There are a few public boats at the PBC you could booby trap without drawing notice but there is no guarantee you target would take them out on the water.
It makes more sense for a sniper to take the rower out from the shore. There is plenty of cover on both the DC and Virginia banks and there are lots of ways in and out. The assassin could even wait for one of the planes on approach to Reagan if they wanted to hide the rifle’s report. But if they wanted to keep the killing dramatic, it would be more effective to row by in another boat and throw a stick dynamite than to hide a bomb in the boat. I assume that’s what the female rower is doing in the video. Also, underwater mines would work too.
Or, since most rowers are also urban bike riders and this is happening in Washington, an assassin could just run the target over with a car. I don’t think that’s illegal in DC.
Which reminds me – you know how the taxi’s in DC say Washington Cab Ass’n or something like that on the door? Wouldn’t it be awesome if Ass’n stood for assassins and not association? That would make some great television watching. Not some crappy boat blowing up some stuck up rowing nerd from Georgetown working at a K Street law firm for jerks.
Update: per Tom's suggestion...
Torpedoes were considered. However, that stretch of the river would extraordinarily difficult to navigate by submarine. When the city built river walls decades ago, it greatly disrupted the natural depositing on sand and silt along the banks and during times of little rainfall, you can see how shallow the river is on the Virginia side. Additionally, while the Three Sisters formation is the most obvious rock hazard, the District side is dotted with large, underwater stones.
An air delivered torpedo would also be difficult to pull off. Even if the pilot was able to avoid detection due to the FAA’s Prohibited Area no-fly-zone around the Potomac, they’d have to thread the needle under Key Bridge to deliver the torpedo.