Marina Retreat is on the third floor of a building in Milford Haven marina. It's a flat, so it's an apartment, not a cottage. You get good views of the boats coming and going from the main living area.
It sleeps six with three bedrooms. One of them is up on a mezzanine level above the living space, so it's open to the room below. There's one bathroom. The place has a 4 Star rating. It's modern and clean.
You're right on the marina. There are a few restaurants down there, some do fish. The town centre for shops is about a ten minute walk.
For beaches, you're looking at a drive. Barafundle Bay and Broadhaven South are about forty minutes south. They're very good. The National Trust Stackpole site there is worth a look for walking.
Inland, Pembroke Castle is about ten minutes by car. For family days out, Folly Farm and Oakwood are within half an hour.
The facilities include a washing machine, dishwasher, and parking on site. Bedding and towels are included. You can bring one dog.
A couple of useful links if you're planning: Pembrokeshire Coast National Park and Visit Wales Pembrokeshire.