Easier from a boat. Just let down until it hits bottom and reel back up a bit.
Casting from a pier or the jetties themselves is harder. You need weight to keep it down, but then the current pulls the line into rocks.
You need some current for fish to bite, but too much and your line gets into the rocks.
I try and find a spot where I can just let down a weighted bait in the current and keep it off the bottom. Usually the end of a pier or a bend in the rock line.
“Which of you, if your son asks for bread, will give him a stone? Or if he asks for a fish, will give him a snake?" - The Messiah