Professional Construction Products

Developing high performance construction products through extensive research and testing.

Underwater Sealant

(Last Updated On: 3 June 2023)

Underwater Sealant

Adiseal is such a great product that it can be used as a dry or wet sealant, underwater sealant & even underwater glue. Most sealants require the surface to be dry for it to stick to the surface. With Adiseal, it can be applied to dry, damp, wet surfaces and even underwater. This makes Adiseal ideal for carrying our permanent and emergency repairs in pools, boats, buckets, tanks, tubs, leaking gutter, felt roof and many other items. This article will also look at how to seal underwater and how to glue underwater.

Underwater sealant. Best in independent test.

Sealants suitable for use underwater

As most sealants have to be applied to dry surfaces, it can make the job much longer to complete if working on something that contains water. The water will need to be removed first to be able to apply the sealant. This can take a long time where there is a lot of water, like in pools. Even if the sealant is applied to a dry surface, not all products are suitable at sealing underwater when the water is reintroduced. The products might not stay bonded to the surface underwater.

Underwater sealant sealing leak in water.
Underwater sealant demonstration of sealing leak underwater.

Adiseal is best underwater sealant

Adiseal waterproof sealant and adhesive can seal a leak even underwater. To show how good Adiseal is at working underwater, a 10mm by 250mm hole was cut into a large tub. It was then filled with water. Even with the water pouring through the large hole, Adiseal was able to seal instantly.

Video of underwater sealant sealing a leak underwater instantly.

For a product to successfully seal underwater, it also needs to cure underwater, resist mould growth as well as stay stuck to the material surface.

Best mould resistant sealant test

To find out what is the best underwater sealant, we carried out several tests including a mould resistance test. The test was carried out by applying different sealants inside new plastic cups. The cups were then filled half way with tap water. Each cup was then covered and kept in the same conditions, to be fair to all the products being tested. The best sealant was Adiseal as it had the strongest mould resistance from the sealants tested. This can be seen in the image below.

Mould resistant underwater sealant test. Adiseal vs popular competitor. Adiseal has strongest mould resistance underwater.
Strongest mould resistant sealant test results when in water.


Mould resistance test result

Even after 90 days of being underwater in the same tap water, both the sealant & water are still very clear in the Adiseal cup.


Clear sealant

Adiseal Ultra clear sealant & adhesive is one very clear sealant. Other sealants might say clear on the tube but when you apply them they are instead cloudy or have coloured tint. Cheaper silicone sealants tend to be very cloudy, almost white in colour when you apply them instead of being clear.


Adiseal Ultra Clear has strongest colour retention underwater

Clear underwater sealant in water comparison. Adiseal Ultra Clear sealant vs *** sealant and adhesive. Adiseal has stayed clear whereas *** sealant and adhesive has turned white.
Colour retention of sealant test in water. Adiseal Ultra Clear vs *** sealant and adhesive.

Adiseal also has the strongest colour retention when underwater. As the image shows, the competitors clear product has turned white whereas Adiseal stayed clear.


Colour retention test

The colour retention test was carried out with a number of clear sealants from different manufacturers. Each product was applied inside new clean plastic cups, filled half way with water, covered & kept them in the same conditions.

Clear underwater sealant test in water. Adiseal Ultra Clear sealant has stayed clearest in water. Popular competitor *** sealant and adhesive has turned white.
Clearest sealant test results when sealant were kept in water.


Colour retention test result

Adiseal was the only product to stay clear above & underwater, making it ideal for use as an underwater clear sealant & glue.

Adiseal is available in the following colours:

It can also be manufactured in any RAL colour.

Other Benefits of Adiseal Underwater Adhesive & Sealant

  • Works in dry, wet, even underwater
  • Good initial grab (for even more grab, use the other Adiseal colours or Adiseal Hi-Grab)
  • Gap filler adhesive
  • Resists mould
  • Over paintable (paint can be mixed into Adiseal Ultra Clear to make custom coloured sealant)
  • Non brittle
  • UV resistant
  • Virtually odourless
  • Isocyanate free
  • Solvent free
  • No shrinkage or cracking
  • Flexible adhesive
  • Prevent fungal growth
  • Prevent bacteria growth
  • Indoor and outdoor sealant and adhesive
  • Good resistance to chemicals
  • EC1 Plus certified
  • ISEGA certified – safe for use in food preparation areas
  • Suitable for internal & external use

The standard adhesive drying time for Adiseal is 24 – 48 hours to fully cure. Curing times can increase in colder temperatures.

How to seal underwater

Details of how to seal underwater.

  1. Pick suitable sealant

    To seal underwater, most sealants are not suitable. Adiseal will be able to seal in dry, damp, wet and underwater.

  2. Clean surface

    To get a good long lasting seal, making sure the surface is clean is vital before applying the sealant. If there is any grease, dirt or mould, clean that first before applying the product.

  3. Apply sealant

    With Adiseal simply apply it to the area that requires sealing.

  4. Seals instantly

    Although Adiseal can take 24 to 48 hours to fully cure, it should be able to seal straight away.

  5. Remove excess

    Remove any excess sealant to get a good clean finish. This can be done whilst the underwater sealant has not cured yet. If the sealant has already cured then cut the excess off with a sharp knife.

Wet Sealant

Adiseal seals, grabs and bonds in dry and wet conditions. The grab properties and wet sealant properties of Adiseal, were demonstrated by pouring water on bricks first. On this wet surface, the wet sealant was applied, grabbed and lifted with another brick immediately. This is just one of the reasons why Adiseal is also a great wet weather sealant.

Applying wet sealant on wet brick.
Applying wet sealant on wet brick.
Grab demonstration of wet sealant on wet bricks. Ideal for use as an underwater glue.
Instant grab demonstration of wet sealant on wet bricks.

Underwater glue

Adiseal is both sealant and adhesive in 1 product. For this reason it is also a great underwater glue. As shown above, Adiseal grabs instantly in the wet. It also cures in wet and provide the strongest underwater glue bond. In an independent adhesive strength test, Adiseal was way ahead of competitor products. For more information visit the Adiseal adhesive & sealant page.

How to glue underwater

  • To glue underwater requires a special adhesive that can be applied underwater, cures underwater and the joint remains strong in water. Adiseal waterproof adhesive & sealant is able to glue underwater.
  • Making sure both surfaces are thoroughly clean will get the best bond. Clean any grease, dirt or mould from the surface of the items that require sticking underwater.
  • Apply the underwater glue to 1 surface and push the other item on firmly.
  • It can take 24 to 48 hours for the adhesive to cure so temporary supports might be required to hold the items in place.
  • Remove any excess to get a clean finish.

Where to buy underwater sealant?

In the UK, the underwater sealant can be purchased from Adiseal stockists. For other countries, it can be purchased from online sellers like www.guglue.com who can ship worldwide. Please contact us for further details of where to purchase from or enquire about the exclusive distribution opportunity for your country.

Frequently asked questions about underwater sealant

What is the best underwater sealant?

Adiseal is the best underwater sealant. It works in dry, damp, wet and even underwater. It seals instantly, has the strongest mould resistance and colour retention underwater.

Where to buy underwater sealant?

Underwater sealant can be bought from Adiseal stockists in the UK. For other countries it can be bought from online sellers like www.guglue.com

Does Adiseal underwater glue cure in water?

Yes Adiseal is both sealant and adhesive. It was the strongest adhesive in an independent test. It will glue many different items underwater and cure in water.

What product can be used as an underwater adhesive?

Adiseal can be used as an underwater adhesive. It works in the dry, damp, wet and even underwater. It remains waterproof and has an extremely strong adhesive strength bond.

Suhail Matadar has extensive experience in the construction industry as an electrician, involved in installing, inspecting, and testing electrical systems in various projects. He excelled in sales, working for a major UK wholesaler, selling construction products to professionals and the DIY market. Suhail's background includes working at a leading home emergency repair company dealing with trades people. With a BEng (Hons) degree in Electronic Engineering, Suhail has worked with PLCs in the nuclear fuel manufacturing industry. During his studies, he gained practical experience at a chemical manufacturing company known for producing award-winning cleaning, hygiene, and livestock protection products for over a century. Currently, Suhail runs a global business specialising in supplying, researching, testing, and distributing chemical construction products like adhesives and sealants.