It is walkable, but it is a really long walk.
As you get off the ship (or through the local vendor area, I can’t remember) there will be people there offering rides to Eagle Beach, but you will have to wait until they fill their vehicle (open air safari truck type thing).
There are taxis that can take you. Some will take a card, otherwise US cash is fine. Some will offer to pick you back up at a particular time, but keep in mind they will not want you to be wet and sandy.
The local bus system is also really reliable and the terminal is not far from the port. You can pay per trip (2.50), buy a retour card (round trip) or an all day pass for $10.
There are vendors at Eagle Beach that rent chairs or you can bring your own.