i need the The boat moving when my character jump on it

The issue is OnTriggerEnter2D() executes once but you intend for it to execute continuously.

The easiest fix is to rename OnTriggerEnter2D to OnTriggerStay2D. This way the function will be called as long as the player touches the trigger and allows the boat to move towards its destination.

Alternatively, you may consider starting a coroutine inside OnTriggerEnter2D to perform the MoveTowards or set a flag that gets checked inside Update.