Close-fitting clothing (cycling/running/yoga style) so it won't get caught in moving parts of the boat. Layers on top, so you can adjust for weather and intensity of workout. Tech fabrics or wool (not cotton, which makes you lose body heat rapidly when it's wet from sweat or splashes). Thick socks to wear in the boat. Hat (for sun protection or warmth). Shoes you can easily remove and leave on the dock.
For other boats to avoid you, they have to be able to see you. Please wear light or high visibility clothing, especially in dim light.
PFDs are not required. Traditionally rowers did not wear PFDs, as they interfered with the rowing stroke. In recent years, some rowers are wearing inflatable belt packs, especially in cold water. New styles of slim profile PFDs that don't interfere with the stroke are increasingly available.
Per Transport Canada rules: Rowing shells attended by a safety boat are not required to carry safety equipment, provided the accompanying safety boat is carrying enough PFDs for each person in the largest rowing shell that they are accompanying.
It's your choice.
We row racing shells, not coastal or wide-body boats. Most of the time we scull in singles, doubles, and quads. On occasion, we roll out an eight, straight four, or a pair for sweep rowing.