What is great about this ceremony is that it happens right as a Sprint closes, meaning fresh ideas are usually top of mind and able to be teased out by the whole team.
There are several great retrospective techniques in the Agile community, the one we are going to see today is called Sailboat Retrospective as it uses a sailboat as a metaphor for the team.
The idea is that the team is on a sailboat, heading towards their goal while dealing with winds and rocks along the way.
Winds help propel the boat forward, but obstacles such as rocks and stubborn anchors represent the risks that the team might encounter and that could slow them down or even stop them from getting to where they need to be.
Let's look at the process step by step.

Step 1: Set the stage
The facilitator draws a large picture of a sailboat floating in the water, with about half of the space above and half below the water/boat, then adds anchors, wind, rocks and an island.
He/she then explains that we're going to use the sailboat as a visual metaphor for the team.
Moreover the facilitator explains that, on a sailboat, there are things that slow it down (anchors), and things that propel it forward (wind).
Note: the facilitator could let the team draw the picture of the boat, it helps to act as an icebreaker and get all of the group participating and on the boat.

Step 2: Add goals
The facilitator asks the team to write down what their vision is, what they want to achieve, and what is their goal (this is represented by the island).
Examples can be: the best development environment they can imagine, an effective team who can take pride in their work, filled with happy customers, opportunity for learning and growth.

Step 3: Gathering data
The facilitator then asks the team to think of what is anchoring the team down and what is propelling it forward, and to start writing one anchor/wind per sticky note.
Sometimes people will be unsure if they should gather a bunch of stickies and then come up, or just bring them up as soon as they have one. I encourage the latter. As a facilitator, just keep an eye out for the energy in the room - you may need to prompt someone to go ahead and put their items on the board. When the energy starts to die down a bit, give people a fair warning that we'll wrap this part up in a moment.

Step 4: Generating insights
The facilitator asks the team to come up to the board and group sticky notes that seem related somehow. As they do it, the team is asked to read the sticky notes out loud. This part is a bit of a self-organizing activity, it may need a bit of facilitation to make sure that people are getting some value out of the grouping and that one person's opinion isn't dominating when creating the groups. The key here is engaging group discussions, awareness and consensus on what the sail/anchor is and how it impacts the team.

Step 5: Plan next steps
Remember to celebrate success and plan action items for current and future obstacles that have been identified during the above brainstorming.
Finally, the facilitator can ask team members to "dot vote" for the group or individual sticky they think should be worked on.
Total up the sticky/group with the most dots, and move into some root cause analysis and proposed changes to make!
Note: I typically give everyone three votes, and they are allowed to use them however they please: place all votes on one sticky/group, distribute them around, or even don't use one.

Enjoy!

Source:
The idea started from Luke Hohmann, who presented it as one of the innovation games in his book “Innovation Games”. Over the years it has been modified a few times by many in the community.