Yes! The mother of indoor rowing competitions is the CRASH-B Sprints, held annually in Boston. The Charles River All-Star Has-Beens started when the U.S. boycotted the Olympics in 1980 — during the same era that Concept 2 launched their Model A; necessity met opportunity. CRASH-B is still held with aplomb and doesn’t require any special qualification of its applicants.
On a rowing machine, you don’t want to be wearing clothes that are too baggy as the fabric can get caught between the seat and the beam it slides on.  It’s not a disaster if that happens, but it can get annoying if your shorts keep getting caught there while you’re trying to get a serious workout.   It’s better to wear shorter, tighter-fitting shorts (nothing ridiculous), but just enough to ensure it doesn’t the material doesn’t hang down.
In sweep or sweep-oar rowing, each rower has one oar, held with both hands. This is generally done in pairs, fours, and eights. In some regions of the world, each rower in a sweep boat is referred to either as port or starboard, depending on which side of the boat the rower's oar extends to. In other regions, the port side is referred to as stroke side, and the starboard side as bow side; this applies even if the stroke oarsman is rowing on bow side and/or the bow oarsman on stroke side.