Hi John,
as long as you don’t pick nylon or nylon based materials you are pretty much good to go. I would personally choose Polyester or Polyethylentherephtalat (known as PET) as examples: Colorfabb XT or Taulman T-Glase).
Both have nearly no warping, are durable, a little bit flexible (but not elastic) and are available in different colors as well as clear.
Another cheaper concideration would be ABS. However ABS can warp.
(Beside that I’m european and have no clue regarding american measurements, what means one ’ and what mean two of those ‘. I know that 2" means two inches, but is 1’ meaning one inch and you just left out the second line or does it mean feet or whatever 
)
You could even use PLA, however PLA is biodegradable and will maybe rot when permanently in contact with water.
Anyways PE (especially PET) would probably be the best choise. Those materials also have very good layerbonding so they should stay watertight. Printing in semi-detailed resolution (0,1-0,2mm) with common nozzles of 0,4mm diameter or similar should give you good results.
Colorfabb XT is more flexible and available in more colors (also clear), however T-Glase is stiffer and even clearer, T-Glase is also only available in clear and clear with tinted red, green, blue or black.
If you want to get something even stronger you might want to look towards Polycarbonate (common shortform is PC). This is a very strong material, used in things like windows of cars, protective glasses and everything, where PMMA (commonly known as acrylic glass or plexi glass) is too weak.
Polycarbonate is very difficult to print, it extrudes at 310°C roughly and needs a bed temperature of 100-120°C with a strong adhesive. BuildTak says, that their printing stickers are capable of holding PC down, however this is untested.
An easier-to-print alternative to Polycarbonate is the so called Tritan by Taulman (by the way here’s the link: taulman3d.com).
Tritan is not 100% Polycarbonate, but based on it. It prints colder ( 270°C if i remember correctly ).
Tritan is still in a kind of semi-beta phase, meaning it’s rarely sold ( e3d-online.com has it) and Tritan isn’t extensively tested jet, however Taulman materials are usually of very high quality. Look for “thomas sanladerer” on youtube, he has made a review about tritan. The beta version of tritan that he was testing had poor layer-to-layer bonding for thin parts like vases, but for thicker parts, like a 5 perimeter shell this should be all good.
By the way, Colorfabb’s XT and Taulman3d’s T-Glase are both food safe.
I hope this helps you,
Marius
