Cletus; Here you go.
https://www.militaryfactory.com/modern-navy/islamic-republic-of-iran-navy.asp
Shows 1 coastal Diesel Electric 8 attack submarines. (all torpedo, no missles.)
https://www.militaryfactory.com/ships/detail.asp?ship_id=Kilo-Project-877-Paltus
A suicide mission with a a large nuke on a private boat on the Potomac river, or whatever river runs by MaraLago, would probably be enough to kill the President. (And any other politicians and Judges/Justices in DC at the time.) There are also the those cargo container missles that might be in some nearby port....Baltimore or Philadelphia or? (I am not eastcoaster...)
Thanks.
Both Tom Clancy and Vince Flynn wrote if such a scenario.
The Potomac is in DC, MD and VA.