RRR="red, right, returning," so, red on the right when one is returning. Red will be on the left when leaving the bay or harbor.
They are channel markers and tell mariners where the channel lies
Preferred channel markers are buoys showing red and green bands.
To mark the shipping channel.
Keep the marker to your port (left) side. Heading down stream it'll be to starboard. Usually there will be a red marker to the starboard headed upstream, and you should keep between the buoys , sometimes there will be midstream buoys, or even preferred channel markers, marking safe deep water channels. They will be red over green, triangular, lettered or even numbered for starboard markers, and green over red, square, lettered or odd numbered for port side markers. Center channel markers may be yellow or white, hazard markers are black over white, or black over red. Inter-coastal waterway markers are yellow. States have their own marker systems, heading up current though in all systems will be green to port, red to starboard and black marking hazards. Lighted markers follow the same rules, green to port, red to starboard and white for hazards heading in from the sea/ocean. If the lights are moving they're on a vessel, stopped or anchored vessel should only show a white light or lights. Yellow lights indicate a vessel under tow.
When returning to the harbor, you will see a green light on the left side of the ship channel and a red light on the right side of the channel. Go outside those lights and you may run aground onto the bottom in shallow water. Just remember this old adage: "Red on Right when Returning". The opposite is true when departing the harbor to go to sea, i.e., red light will be on the left and green light will be on the right.
When returning to the harbor, you will see a green light on the left side of the ship channel and a red light on the right side of the channel. Go outside those lights and you may run aground onto the bottom in shallow water. Just remember this old adage: "Red on Right when Returning". The opposite is true when departing the harbor to go to sea, i.e., red light will be on the left and green light will be on the right.
When returning to the harbor, you will see a green light on the left side of the ship channel and a red light on the right side of the channel. Go outside those lights and you may run aground onto the bottom in shallow water. Just remember this old adage: "Red on Right when Returning". The opposite is true when departing the harbor to go to sea, i.e., red light will be on the left and green light will be on the right.
Red to the Right, Returning. Keep the red buoy to the right side as you enter the channel.
The red light on a plane is on the left side
This is a channel marker, placed on the edge of a channel. Green markers will always have an odd number on them. If you are heading upstream it should be to your left. If you are heading downstream it should be to your right. It will be opposite a red marker or bouy with an even number on it. To aid in navigating, the term "red, right, returning" is used meaning as you return from open waters (head upstream), the red marker, bouy, sign etc, should be to your right. That means the green one, in your example with a 3 on it, should be to your left. If its on your right side, you are outside the cleared channel area.
If you are refering to nautical channels, these are pretty much universal (unlike road laws). The green 'channel' is usually a line of green bouys, markers or poles (with green lights for night) to show the deepest way up a channel or river for boat navigation. The red 'channel' is merely the opposite.
The marker near shore at twilight with a square on it is most likely red in color. Red square markers indicate the left side of a channel when entering from the open sea or heading upstream.