where is it, and how deep is the water, is it an area prone to storms or ice ?
To set your expectations, this bit of north sea is ~ 50-150m deep, never more than about 30 miles off shore and to survey this little offshore loop is about 3 months.
Deeper water or poorer weather make it harder. A straight flat run is faster. A lot more info needed to answer, and you'd do better to get a quote.
