White or Basking?
 

Great view at 0:38. I'd guess a white shark. Don't think basking sharks have that bold contrast of color.

Neither, Looks to me like a big Dusky.

Don't really get duskys in and around cape ann, not to say it couldn't be. I send along to Skomal to get his thoughts. There is a small colonly of seal that haul out at the salvages. Cool all the same.

small basker.
pause it at :37.. if it was a white, the dorsal would be in line with the back of it's pectoral {its armpits} Or, Directly above it's armpit the dorsal would start.
Those pectorals are set forward= Basking shark.

I am going to say basking, just due to the discrepency in the tail fin. Top appears to be much longer than the bottom portion (just my observation based on trying to slow the video down).

Either way it is a cool experience!!

IMHO dosal is too high an the body color is wrong for a basking shark. Could also be a big brown (It's hard to tell duskys from browns) but I've never seen a brown that big.