After 22 years of trying different tapes I came across this one in a search. Anyone that needs trans-dermal patches and has trouble keeping them stuck on needs this. It is super thin and requires extra care to place but once seated correctly it is the best. Shower, tub or pool, it just laughs at the moisture and stays dry.
I highly recommend.

I have had multiple skin biopsies and basal cells removed, and the toughest part was often the post-procedure dealing with keeping it covered for days/weeks. I tried all types of bandages, but my skin is very sensitive and reacted very badly to everything I tried. I'd get bad rashes and swelling from the adhesive, not to mention being very itchy. Then I tried the Tegaderm patches from the store and they worked great. So I then ordered this roll and have been cutting to size to fit. They work great! Little to no skin irritation and they really stay put, even when swimming. Generally water proof - I can tell since I use non-stick gauze underneath and it is usually dry after swimming even a few hours. A little tricky to use at first (as are Tegaderm patches), but once you get it down it works great. They do stick well and are a little fussy removing, but do not hurt removing although I use a non-stick gauze pad, so the the Tegaderm is not directly contacting the healing wound in my case - I can't comment how this would be if directly contacted the wound. Would recommend for those very sensitive to band aid/adhesives.

I use tegaderm to keep my HRT patches on. I have tried all sorts of weekly HRT brands and they don't want to stick for more than 12 hours or so. I did a lot of searching on the internet to arrive at this method, out of desperation. I hope this helps someone. I bet it would work for keeping any other kind of medicine or medic patches secured. Here's my method-
I take a shower but then dry out for at least two hours. I cut a piece of tegaderm that is quite a bit bigger than the patch. I clean the skin area with alchohol wipes. I bend my back or stomach or leg whatever way I need to so that my skin is stretched as much as it can be wherever I'm applying the patch. Then I stick on the HRT patch, and then put the tegaderm over the patch. After peeling off the top layer of plastic, make sure all the edges and corners are stuck down well. I use my hand to warm up then tegaderm so it really adheres to my skin. (I don't really know if that part is necessary but I do it in case it helps.)
I think the MOST IMPORTANT part of this is REALLY bending tonstretch your skin when applying the patch and tegaderm. When I put it on my back, my husband helps me. If you don't stretch when applying them, when you do stretch and bend naturally, the tegaderm won't really stretch enough with you and it can come loose.
The downside of this method is that after a week, it is REALLY sticky and it doesn't feel great peeling it off. I also have to use alchohol wipes or scrub to get the sticky residue off. Also, my skin under the tegaderm feels dry so I use a serious drugstore type lotion like CeraVe, Aquaphor, or Eucerin to repair the dryness. These are annoying side effects of using the tegaderm this way, but I if I want to keep patches on, it's the only way I can get them to stay in place. I hope this is helpful.

My wife had to have a hip replacement and the doctor wanted the incision area to stay dry for 6 weeks, this product was the ticket! By placing it over the gauze pad she was able to take a shower from day 1 without worrying the wound was getting wet. Very pleased with this product! The box says "Made in Germany" in case anyone is wondering.

Update to this review: On a whim, I tried rubbing the edges of a piece with thumb and finger, the way you can do to open a plastic bag, but that doesn't work because of the rigidity of the #2 layer. But I then blew gently on an edge of the roll, and the warmth and moisture of my breath allowed me to separate the #1 layer from the sticky Tegaderm portion and attach the film to my skin, something that other disappointed purchasers might want to try. As it happens, the roll doesn't work as well where I want to use it, on my knees (not quite wide enough and doesn't adhere well because of joint movement), so I'll return to the Tegaderm dressing version, which works superbly, despite the cost. But since my problem with this roll was user error and not the fault of the product, I'm revising my rating to five stars.

I've successfully used the Tegaderm dressing version for years, but I found it impossible to use this roll, despite the very helpful explanation provided by reviewer LongBeachGeorge. I was able to separate the #1 layer with the first piece I cut (the end piece of the roll) and attached it to my wound, and readily removed the #2 layer. But with subsequent pieces, I found it impossible to separate layer #1 from the sticky Tegaderm patch layer despite spending fifteen minutes or more trying to do so with several different pieces. I believe that I have normal dexterity so i find it puzzling that I cannot accomplish this. Perhaps the "one-star" reviewers are having the same problem I have, leading them to conclude that the product doesn't have the three layers it's supposed to have. I would agree with them--except that I was able to use the first end piece successfully. There must be user error here, but I can't figure it out, so I'll just have to go back to the dressing version, which works perfectly. And I recommend the one-star reviewers try the dressing version, which, while more expensive, is easy to use. To give the product one star seems unfair, since it may be my fault, so I waffle and give it three stars.