Visibility is usually best at high water slack, three hours after high water Portland. Low water slack is two hours before high water Portland. There are no convenient transits, so you need to search with a GPS and echo-sounder. It's a big wreck lying across the current with its stern towards the shore. Slips are available at Weymouth, Portland, Kimmeridge, Swanage and Poole.
Campsites are out of town, usually very smart and a bit expensive.
Admiralty Chart 2610, Bill of Portland to Anvil Point. Ordnance Survey Map 194, Dorchester, Weymouth and Surrounding Area. Ordnance Survey Map 195, Bournemouth, Purbeck and Surrounding Area. Dorset Shipwrecks by Steve Shovlar. An impressive modern wreck with lots to explore.