Launch into the current (i.e. with the bow of the boat pointing upriver) if at all possible. Get bow pair's blades on the water as soon as you can, especially the one closer to the dock. This might mean having bow seat or two seat draw their oar through the oarlock and push off the dock with the tip of their blade while everyone else sets the boat. Add pairs one at a time from the bow until you have enough speed to get out into the river. Peek back at your stern to make sure it doesn't scrape against the dock as you're pulling away.
Upriver Side: Lean away and walk the boat all the way to the end of the dock. Add pairs from the bow as soon as they can get their blades on the water. Getting the boat moving as soon as possible will help you avoid getting the stern pushed into the dock by the current.Downriver Side:
Have everyone in the boat shove off the dock at the same time. Start with the boat as close to the dock as possible, and lean away slightly to avoid snagging the bottoms of the riggers on the dock. A good call for this is, "Lean away… Ready to shove… And shove!" The current will help you get the boat away from the dock. If you don't get far enough away for all of your rowers to get their blades on the water, have someone from the bow four (or bow pair in a 4+) draw their oar through the oarlock and push off the dock with the tip of their blade while everyone else sets the boat.
Use your rudder to make small adjustments to your line, but keep in mind that the boat steers from the rear; if you steer to port, your stern is going to move to starboard. If you're very close to the other boat, use the rowers in the bow to pull you away instead of the rudder.
Water moves faster through bridge arches than it does elsewhere in the river. The more space in the river the bridge abutments take up, and the faster the current, the more pronounced the effect. Bridges built on columns can have almost no effect on the flow of water underneath them, but old-style arched bridges where the solid part takes up a significant portion of the river (such as those on the Charles River) can toss your boat around as you go through them. Luckily, the pattern of the current in these situations is fairly predictable.
Water tends to funnel into the arch and then funnel out again symmetrically. It will push your bow toward the center of the arch as you enter, and then push your stern toward the center of the arch as you exit. If you're prepared for this, you can use the current to your advantage and move from one side of the arch to the other as you row through it (the Eliot bridge is the perfect place to do this as you pick up the turn to starboard for the final stretch of the Charles course).
Generally, best the way to cross the river (partly because it makes your intentions predictable to other boats) is to make a 90-degree turn, row straight across to the other side, and then make another 90-degree turn.
If possible, plan ahead so you can make your turn while the boat is still moving. As soon as your rowers weigh enough, have the sternmost person on the side you want to turn toward sit at the finish and check it down, digging their blade deeper into the water as the boat slows down. Once their blade is fully buried, have them take one long, slow backing stroke. You can have one or two people in the bow on the opposite side add in with normal strokes until you've completed the turn.
It's easier to pull this off if you explain the maneuver to your crew ahead of time because the instructions are too wordy for an in-the-moment call.
In two, weigh enough and stroke seat hold water
Two--weigh enough, stroke seat hold
...and back it
Your momentum is what's powering this maneuver, and having one whole side hold water slows the boat down too much before the turn is completed. The sternmost person on the side you want to turn toward has the most turning power (when holding water or backing; the opposite is true for forward strokes), so you get the most out of your momentum when you have that person be the pivot point. If you're moving too fast to pivot around one blade (in an 8+), you can have the two people in the stern on that side (six and stroke or five and seven) check it down.
That's where their blade is closest to the centerline of the boat and therefore has the most influence on the boat's direction. This is the same reason there is one rudder in the middle of the boat instead of two smaller ones on either side.
It's a good idea to spin in the direction of the traffic pattern; if the traffic pattern is counter-clockwise, you should spin counter-clockwise. There are two major things to remember when you're turning 180 degrees in current:
The simplest way to turn without deviating from your line down the river is to come to a stop, then alternate one whole side backing with the other side rowing. You could have the backers and the rowers go at the same time (instead of alternating), but when you do that they tend to bump into each other as they move in opposite directions up and down the slide.
This is NOT something you should try on race day or if your coach and crew aren't fully--er… on board. A river turn is when you start on one side of the river and make a complete 180-degree turn without stopping. Plan your whole line ahead of time, including where you want the boat to be at the end of the turn (most likely the other side of the river, because these boats make wide turns, and because that's usually the correct place to be for the traffic pattern). Have the rowers who will be on the inside of the turn shorten to three-quarter slide and the rowers on the outside lengthen out a little bit. Warn the inside-of-the-turn rowers that they may have to lower their hands a tad to keep the boat set and use full rudder until the turn is completed.
Approach the dock going the same direction as when you launched (into the current). Aim your bow at a 30-degree angle toward the point of the dock that you want to end up next to your stern, and drop pairs out one at a time from the bow until you're left with just the stern pair. Some people like to finish with stern pair rowing arms and body only, but you may end up slowing down too much before you reach the dock if the current is fast. When your bow ball is about 3-5 feet away from the dock, have your stroke seat (in a port-rigged boat) hold water. It's a good idea to warn the person in advance that you're going to need them to instantly check it down, since the margin of error here is pretty small.
Try to snag the upriver side of the dock if at all possible. This will allow the current to push you toward the dock instead of away from it. Aim your bow at a very small (maybe 10-degree) angle toward a spot about 10 feet past the corner of the dock (more if the current is faster). Use your stern four, and then your stern pair, to bring you carefully but quickly to the dock. If you need to make an adjustment to your point, use your middle four because they are less likely than the bow pair to oversteer.
This only works if you're close enough that the dock-side blades are already on top of the dock; if you have to lean away to get those blades up, no one on the other side will be able to get their blade out of the water. If you're too far away, back up or loop around and try again.
For simplicity, let's say we're talking about a standard port-rigged 8+ that is parallel to the dock. Have six seat go all the way to the top of his or her slide and use just their inside hand to get their blade as close as possible to the hull. Then have them take small, chipping strokes to push the boat sideways until you're close enough to grab on.