Front-mounted Swimming Snorkel (by Finners): to break down your mechanics into bite size pieces and work on each individually. It eliminates the head movement.
Buoy. Used for pulling.
Ankle Strap. Eliminates kicking while pulling.
Paddles. Mostly beneficial for elite athletes. Not necessary for regular athletes like me and you. The purpose is to desensitize the hand and give the feeling or forearm engagement and creates facilitate high elbow.
Bouncy Shorts. They give you extra floatation. Used on recovery days.
Stretch Cords. For on land training. Great for warming up before the race.
Fins. The right fins should be made from sturdy material on the sides, so they’re not too playable, medium length and the blade that’s playable. The main reason for use is to promote recovery. With long bike and run sessions they are great to facilitate recovery of your legs. The another reason of use is to learn the proper mechanics of kicking.