I live on the island and use Avon skin so soft for the no-see-ums and it works well. Not effective against skeets. Not sure about sea lice as I am not sure what they are exactly.
Sea Lice are basically Jelly Fish Larvae that cause painful rash when you swim. The west side beaches on AC have them sometimes. Some seasons are worse than others from what I gather... but figured if this stuff works, it might make swimming on the best beaches worth it.