Would somebody be kind enough to recap ELT and CVR/FDR ULB ranges underwater and if working what type of equipment would be able detect them?
An ELT won't work underwater. It's 406mhz radio waves won't travel through water. It is for use above the water or on land. The ULB is a 37.5khz buzzer, and it's sound waves, under good conditions, can travel about 2 miles. The sound is too high for a person to hear, so specialized equipment is used to convert it to human hearing range in order to detect it.