In Jersey you can normaly expect 16 degre sea temp, and 20+ air temp in july, we have lovely beaches and coves, lots of places to visit including maritime museme and a offshore (at high water) castle, you can can spend all day in the sun traped bays, and 10 miles of north cost head land foot paths to walk. hotels by the marina. www.jersey.com
there are lots of ribs in jersey showing there versatility for visiting the smaller islands including plateau des minquies and les ecrehou, sark etc. can't go wrong. also loads of very good restrants.