Wrecks are in abundance in Scotland and in Orkney feature mostly German World War II vessels dating back to 1918 which is when they were scuttled in Scapa Flow. Oban is also home to many wrecks although UNESCO World Heritage Site St. Kilda is simply stunning underwater.
Bring a dry suit and experience reefs dating back two million years including the MacLeod's Maidens on the Isle of Sky, and wrecks going back to 1800's including The Wallachia British steamer with cargo still on board and still perfectly intact and The Stassa a Panamanian freighter.