Ostomy Secrets has lace like under garmends that might interest you.

A gal in a support group said she swims in the Gulf of Mexico all the time with no problems. 

I went thru covering my appliance while taking a bath and in the hot tub. I ultimately discovered there is no need to do anything. You can simply dry off the tape on the appliance with a blow drier.

I bought a swim wrap that holds my bag in place from Ostomy Secrets. They have periodic sales. Their prices are high but they are about the only show in town. I wear their underwear but not at the $24.95 per each price. 

FYI -Ostomy secrets has a 40% off Sale going on right now. Not all items are on sale but I just ordered a wrap and another pair of underwear. The wrap is good for under swimsuits and when exercising.

Although I haven't had an ostomy in 54ys I have a k pouch that occasionally needs to be hooked up (and the stoma covered for certain activities )

I am handy with a needle and thread as well as having a wide imagination when it comes to creating clothing that works for these occasions.

If you have a bathing suit that is rather thin, a nice fabric but a bit 'used' or no longer adequate for your body, don't throw it out...cut out the crotch from the bottom, fold it under and hem it to make a tight, swimmable abdomen cover (kind of like a spanx tummy tuck thingy...don' t know the name exactly) that you can wear under another bathing suit to hold your bag tight, in the hot tub or any other wet zones.

I did the same with some stretchy, sexy undies and one piece body suits...In the days of snappy crotch 1 piece lingerie, it made a huge difference to my personal comfort zone...I had sexy, silky lingerie that covered everything nicely (I would just unsnap the crotch until they invented large, wide garter belts that covered the whole abdomen...then I would just remove the thingies that held the stocking up and keep what looked like a sexy, extra wide belt)...I am very, very self-conscious about my abdomen and stoma so the lingerie gave me the freedom to feel 'normal'...and not reveal too much before I was ready...I even managed to maintain very long term relationships with guys who never figured out that I had a stoma unless I was ready to tell. One of them I ended up marrying. (finally had to tell him after a few years...he had figured it out by then and didn't care)

Sharon

Great ideas Sharon. I am digging out my old swimming suit and sewing Machine! 

I know this is a late reply, but when I had my osomy the stealth belt was my saviour. If you look it up you should find the website you can order them from. They are a little pricey but I had my ostomy for 2 years and only ever needed one. They keep the bag covered, and you can actually empty it when wearing the stealth belt thanks to a zipper pocket! It made sex feel a lot more comfortable and it also opened up a lot more clothing opportunities for me! I seriously recommend looking into it. They can be worn all day and night and are extremely comfortable, plus they have stretchy material so it never feels like your stoma is being crushed or is unable to empty, I even found that when I wore it for prolonged periods of time my output was actually less than before! Hope this helps