After meeting back up with Sam Adams and his friends, you'll go to Boston Harbor for a tea party. When you arrive, there will be two large ships in the harbor loaded with tea and Red Coats. You need to first kill the 15 guards on the ship. If you are careful about it, you should only have to clear out one group of 6 before moving to the larger group of nine. Take your time getting a good position to start the fight and let your assassin meter recharge so you can call for help. This will make the battle much faster and easier.
With all of the guards out of the way, the tough part begins. You will have a man on each ship that you need to protect from Red Coats coming to attack you while you dump tea. You must protect Paul Revere and William Molineux. Paul Revere is probably going to be the tougher of the two to keep alive and he's on the ship that you start on.
Start the fight by immediately throwing crates into the water. At the start, the fighting won't be so bad and you should be able to get five or six crates into the water (7 if you're fast) before you need to go fight. After you kill the first bunch, dump a few more crates in the water and you should complete that constraint. Try to throw the crates over the front left or right rails. You can throw directly towards the front but you want to be careful because you can accidentally land the crate on a small platform just below the front. This would not count.
When you go to fight the first set of red coats, stand on the bridge or pier and wait for them to attack. When they attack, hit the counter button, and then push towards the water before hitting the counter button again. This should throw them into the water but sometimes they stumble before then. Keep trying and you will probably get all three in one go. If not, just do this with the next group too.
To get the last constraint, you need to pick up a musket on a rack or that has been dropped by a red coat and stand on one of the railings before hitting the attack button. You should start the fight by doing this because once the fight has started in earnest, the enemy may be able to deflect your attack. If it's your first attack, however, it will almost certainly get through.
If you can get these constraints out of the way quickly then you can focus simply on protecting your two friends. As the process continues, you'll get attacked by more and more red coats, making it difficult to keep up. Try to use the two broken bridges to cross from boat to boat. Even though they are broken, they make for the smoothest transition, allowing you to get into the fight more easily. Keep an eye on your assassin meter and call Stephane if you get in a bind.
Don't be discouraged if you fail a few times, this is a pretty tough memory. Getting this while completing all of the constraints requires you to perfect the opening and have a pretty good grasp of the combat. When your group has thrown over 100 crates, the memory will end.
