How do you kill a Lagiarcus on Monster Hunter Tri

Use a lance. They give you most mobility in the water. Watch out for when he curls up. you cant block that one. I block advance through other electric shocks and keep attacking. aim for the chest that's where he's weakest. If he goes on land use a pitfall trap and blow him upn with barrel bombs. remember to bring a shock trap and tranq bombs (you usually need 3) to capture him in the water.