U can trap the leedsicthys by using a couple on stone gateframes and lead it with a raft then when it eats the raft (before or after) u just slam the final gateframe(s) and there u go, a trapped leedsichys (make sure u arent the only one doing this and also if it despawns, do it again)
It will attacks rafts so be carful coming across one on a boat.
Also the Alpha Albino Leedsichthys Will give you raw prime fish me when you scrape meat off of it, and killing it will give you The Captains Hat Skin
Listen here boys and girls, for it is story time. Once upon a time on my early game raft with my raptor, I was sailing towards my allies base. Keep in mind this was a modded unofficial server. So I turn around and see two of these chasing me! So, when they attacked us...
My raptor jumped off to fight them. Bless him. I had enough time to sail away, but the raptor never was seen again. Yet, I never got the death message..
YOSHI PLEASE BACK!!
PLANT SPECIES X!!!! Slows them right down. Put one on the back of your raft and not even the alpha can get you unless it comes from straight under. Add a ballista and a captain hat as well for added effect.
One day I went on a trip to herbivore island to get some metal I got a few storage boxes full on my raft and some in my invent. I set of home when one of these swallowed my raft, I lost all my metal and was left encumbered in the sea