This site http://www.seasigns.com/ is a great source. I actually took a $50 class on it and it teaches you about 120 basic signals. Once you learn the signs you take a test as well as practice them for about 1 hour underwater (both translating and demonstrating them). The lady that developed them learned ASL because her daughter is deaf and they always communicated that way underwater. After many inquires over the years she developed this system (which is based some off of ASL and uses ASL rules for the creation of some of the new signs). It is very easy to use and you would be amazed at how much more you can communicate. Many of the signs are very intuitive which lends to their ease of learning.