Underwater Diving Rings

These are not your average rings that sink to the bottom of the pool for kids to bring back up. The goal is to go through the rings like an obstacle course and either see how many you can get through or who can get through them the fastest. These are easy to make, adjust, and setup. Constructing 10 rings will take about an hour or 2 (that's based on me trying to make them while distracted by a movie) and setup/removal of the rings takes about 5 minutes once constructed.

Background:

As of posting this, I am 18 years old and have been competitively swimming for just over 10 years now. I am both Red Cross lifeguard certified (first aid/CPR/AED) and PADI open water certified (SCUBA diving) and while I have helped teach other kids learn better swimming techniques with a coach's supervision, this year was the first year that I would actually be coaching a team. The last week of the our summer season is spirit week where the kids aren't being pushed as much and the coaches come up with games for the swimmers to enjoy. Since my long course season was over, I decided to create something fun and could be used in multiple ways.

Notes:

While the pictures in the setup show only one bottle per hula hoop, two are needed. Instead of marbles, I ended up using pea gravel from a local park to weigh down the hoops. I used 2 small 12oz (355mL) Gatorade bottles because it was easy to get in a 12-pack but a single 32oz (946mL) bottle could be used instead. Try to use whatever bottles from your recycling but I was short on time and my recycling had just been picked up so I had to buy some and then dumped the drinks into a 1 gallon (3.8 L) pitcher for later.

Also, this is my first Instructable so feel free to give me some feedback!

Supplies

10 Hula Hoops - $20

100' (30 m) Black Paracord - $7

20 Small Bottles (12oz, 355mL) - $12 (2 12-packs)

1 Roll of Duct Tape - $3 (yes, I was out)

Pea Gravel - Free (can be found for $4 per 1/2 cu. ft. or 14 L)

Rubber Bands (optional)

Total Cost: $42 (~$4 per ring +/- $1 depending on what you can find or already have)

Tools:

Scissors

Lighter

Step 1: Purchase & Prepare Materials

Obviously go wherever has the cheapest price but in case you were wondering, I purchased the paracord and duct tape from Menards, the Gatorade bottles are pretty much the same price at every major grocery store (Wal-mart, Meijer's, & Kroger), and the hula hoops were purchased from Five Below but you can try a dollar store or similar.

Make sure the bottles are empty and gather all of your supplies. Go ahead an wrap a 3" (8 cm) piece of duct tape around the joint of the hula hoop to protect and strengthen the hoop. This can be skipped but the hoops are constructed by bending a plastic tube into a circle and using a piece of plastic that is inserted into each end to hold it in it's "hoop" shape and then labels were placed over this joint to hide it. By placing a piece of duct tape over the joint, it keeps the joint hidden and together as the label will likely dissolve in water. This may vary depending on your hula hoops.

Step 2: Fill the Bottles With Gravel

Unscrew the lid and place it to the side. Fill the bottle until it is full, then with your hand covering the top, gently tap it on the ground or shake it. Do this a couple of times and once the gravel has settled, fill the bottle with more gravel. Repeat this shaking process until you are confident that the bottle is full. Repeat this with every bottle.

Step 3: Prepare the Paracord

Cut the paracord into 10' (3 meter) sections and use the lighter to melt the ends of the paracord. Your paracord may be a few inches shorter or longer than 100' so your last section may not be 10'. This is fine as only 2 of the sections will be at full length in this Instructable. The reason why each section is 10' is so that the longest ring is just under the surface of the water (in a pool that is 12' deep) but depth can be changed so that all rings can be at the surface or all rings can be at the bottom. I set the depths so that there would be 2 rows of 5 rings, with each ring in the row at a different depth.

Step 4: Tie the Paracord to the Bottles

Start by tying the "upper" bottle. Leave 6 to 7 inches (~18 cm) off at the end and tie a square knot around the bottle (see images above). Pull it tight and then use the 6 to 7 inches (~18 cm) to tie the "lower" bottle. Make another square knot with about an inch left at the end to pull the knot tight. Once these knots are wet for the first time, you may have to pull on them again but they should stay tight after that. There is probably a better knot for this but this was the easiest one to demonstrate and the one that I remembered at the time.

Step 5: Organize the Bottles and Paracord

Lay the bottles on their side and pull the remaining paracord out so that it is easier to set the depths and finish tying the hoops on.

Step 6: Tie the Paracord to the Hula Hoops

Again, there are probably better knots for this but I wanted it to be simple and easy to adjust. It looks similar to a clove hitch knot but instead of one end of paracord on each side, both are facing the bottom. With the hula hoop towards the top and your paracord coming from the bottom, follow these steps:

1) Over the hoop and then under the hoop towards the right.

2) Bring it back over the cord to the left (still below the hoop)

3) Take the end under the hoop (now above the hoop)

4) Take it over the hoop but under the part that crosses over.

5) Make a knot at the end to prevent the paracord from slipping out.

Step 7: Adjust the Hoops

Adjust the hula hoops to your desired depths by stretching the assemblies out and measuring from the bottom of the bottles to the top of the hoops. My depths were 11 ft, 9 ft, 7 ft, 5 ft, & 3 ft with 2 hoops at each depth. In the previous step you made a knot at the end of your loop in order to prevent the paracord from slipping out; make another knot on each assembly to keep the hoops at the depth you set. If you would like to preset multiple depths for each hoop, start by measuring and making your deepest knots and then extend the hoop to the next depth to prevent changes due to paracord being used in the knot.

Step 8: Wrap Up the Excess

Finally wrap up the spare cord with rubber bands to prevent tangles.

Step 9: Enjoy!

Setup your course however you like but keep in mind the depth as large changes are more difficult to swim through. Make sure they are spaced far enough apart (4 to 5 feet (~1.5 meters) seems to be ideal) and watch swimmers as the complete (or fail) the course.

There may be a large difference in ability so remind them that it's okay to come up for air or skip one if they can't make it. During our races, I was in the middle of the rings with a guard tube and swim goggles to make sure that nobody panicked, got tangled, or started choking (also taking pictures). Although we had a lifeguard on duty, it was a sunny morning so the glare is hard to see through and we were adding something potentially dangerous that many pools could easily not allow.

When disassembling the rings, simply undo the loop that attaches to the rings and wrap the paracord around the bottles and secure with the rubber band. To re-assemble, tie the loop, set the depth, and wrap up the extra cord as shown in the previous steps.

An easy modification would be to have the weights as close to the hoops as possible and with a second piece of paracord, tie a pool noodle to the top as a float. This keeps the hula hoop underwater and sets the depth from the surface with the pool noodle. The noodle acts as a float to keep the hoop off of the bottom and can be used in a lake or other open water.