stern (of ship)
艫 centers on the rear part of a ship: the stern. It is a specialized nautical term for the back end of a vessel.
艫 combines 舟 (boat) with 盧, which likely contributes the sound. The character specifically denotes the stern of a ship.
The left side 舟 is a boat, and the right side 盧 looks like a complex structure at the back. Imagine the stern as the boat's rear cabin or steering area.
For ロ, picture a low stern deck where you can sit and watch the wake: low -> ロ, and the stern is the low back part of the ship.