When choosing the best underwater pond light, there are three things to consider, longevity, lighting effects, and fish safety if you decided to put them in your pond. No such thing as a 100% waterproof fixture. Submersible fixtures are susceptible to leaks. The likelihood of a leak occurring can be significantly reduced depending on the institution and how it is engineered and built. Cheaper is not better when looking for an underwater pond light. Plastic housing can crack from temperature fluctuations and be damaged by the sun.