Re: LL Manta Ray 12 ???
 

Incredible gave good advice! Take it out on the patio on a nice day! Make sure the cement is dry. You don't need to fill it completely. About three to four inches of h2o will usually be sufficient. See where the cement is getting wet, and look above that spot on the kayak. Find the leaks. Some people put the yak a little above the cement, suspending the yak on two sturdy boxes. Mark the leaks with a crayola, or marker. You need a heat gun and a plastic repair (weld!) rod in the same color as your yak. Most manufacturers will send you one. Ocean Kayaks sent mine free! With instructions! Seak the leaks and you're good to go. The number one cause of kayak leaks is the scupper cart! Yaks can't take the leveraged stress these carts inflict on the scuppers when you pull the yak over bumps and sand! Good luck! Piranha

Re: LL Manta Ray 12 ???
 

Small repairs are very easy with a simple soldering iron. You may not even need extra plastic. If you do need plastic look inside your yak - you will usually find some place where you can take a shaving or three without hurting anything. Put the tip of the iron on a suspected seam or crack gently and remelt together. If you actually have a hole, feed in a bit of the plastic shavings.

Piranah's suggestion about getting the same color from your same manufacturer is great because different color plastics and plastics from different manufacturers may not work well together. That said, if I was having trouble finding the plastic I would try some regular milk bottle plastic.

You may want to practice on the milk bottle before you go after your Yak!