Underwater Magic Sealant, 290ml/9.8oz Tube, White

This stuff worked really well for tiles above and below the water level.

I have a decades old fiberglass pools with multiple leaks. The wall has a hairline crack. Easily plugged with this sealant, even under water. I also had multiple cracks in the skimmer. I had to use my finger to apply chunks of the sealant until all cracks were sealed. Now a year later, those seals are still holding up. This product is much better than all other submarine sealants or cements I have tried on Amazon. It really seals tight and lasts very long. There are two drawbacks. First, it is expensive. Second, it is very thick and very hard to push it out of the tube, even with a caulking gun. Once opened, you are most likely unable to use the remaining that is still in the tube. This is why I am only giving 4-star rating. I am ordering a new tube to work on a new leak and add new layers on old leaks.

100% effective and works underwater as advertised.

After watching You tube videos, I used this without a problem, in water and out with great results. Yes, a bit of money, but I don't think I will be doing this again next year whereas the grout had me doing tiles over and over again each year

Used it to seal exhaust ports on a yacht. Worked perfectly byt is expensive.

I checked out several products and read carefully the descriptions. I thought I had a product that could be applied underwater. It said it could be used to patch pool liners while the water was in it. I tried it on our floating dock plastic barrels, but it did not stick at all. I wonder if I could put downward pressure on sealant if it would have worked. I was trying to place it horizontally and couldn't get it to stick. It probably is a good product but just didn't work in my situation.

Really hard to clean off your hands and makes a huge mess but sure does the job. Unfortunately calking gun wouldn’t fit in skimmer so had to use fingers. I used it to patch up some holes in my skimmer and some cracked wall seams. I used some 2 years ago around my headlight and its still holding strong. The smell is also pretty bad but if it does the job I can plug my nose. Adheres very well but pricy!

Does not last more than 6 months. It becomes chalky and it peels off.