DanSinks
Contributor
For cape cod bay, it really helps to have a boat, doesn't have to be a big one. That being said there are good shore dive locations like Sandwich (shallow enjoyable easy dive). As far as the sharks are concerned, since I boat dive, I am much more concerned about finding the anchor line at the end of the dive. Sometimes the current in the bay can be a little more than you expect and if you overshoot the boat on the return trip it makes for a tough swim up current. That said, I have boated all over cape cod bay for years and have not see a GW yet.
I have done a lot of boating around Cape Cod over the last 25 years and have done some diving, I've seen big shark fins near Monomoy Island on 2 occasions(there are thousands of seals beached on this island). My boat has been moored in Falmouth for a few years so have been diving there and will do a lot more. There are a lot of nice wrecks around Martha's Vineyard and the Elizabeth Islands but the current is strong and visibility can be bad. There are no seals close to the north side of Martha's Vineyard so I feel good about diving there, although there was a large great white in one of Falmouth salt ponds a few yews ago.
I just did a google search, there was a person killed last year in Massachusetts by a shark, he was on a boogie board near a seal area, he was the first person killed by a shark in MA in 80 years.
By the way, Having a flashing strobe on the anchor line is a good thing to do to.