This guy can be the easiest tame hands down.. If you want one. Your going to more than likely need tek.. How ever you acquire bio toxin is up to you. On crystal isle in the eldritch isle area. These guys spawn in bubbles. I use my visor to highlight other baddies and kill everything around my target. If it works out just right this guy will have his head hang out the bubble. Just feed him.. Be sure to cryo ASAP piranhas will begin to shred.
Tip: NEVER TAME THESE WITH BIO TOXIN! If you eat the bio toxin on accident, you will faint and die of suffocation and/or creature attacks. You will probably eat it on accident, so don't tame these with bio toxin.
These are passive tames. In my experience trying to tame a 145. You will find having a Basilosaurus will provide you with a mount immune to the shock.
Wear a combination of Riot and Scuba gear. Bring multiple sets. They will destroy your tanks and flippers if you get hit enough times. Lone eels do not deal enough torpor to be a substantial threat with the riot gear.
The hard part is feeding them. They will glow bright blue (without goggles on) when they have built up a charge, and charge you. Discharge a 7 second stun, bite and then flee.
Lure them into an enclosed area. Such as a trap for water tames or a river. This will reduce their mobility and make them an easier tame than in the open ocean. Because they will flee the majority of the tame if they have the room to do so.
-Results of 3/20/17 taming test on Xbox official servers.