Elusive harbor seals at Graves Light

Jim needed deckhand for for his Friday morning charter out to Graves Light so I offered to jump on and crew.  I don’t really crew much on the Keep-AH anymore; I got burned out for lack of variety in scheduled dive sites and to be honest I’d rather be fun diving instead of teaching/crewing.  Still..I do enjoy diving in Boston Harbor and miss some of the regular customers.

He had a customer who just wanted to hire a private guide/DM and also wanted some tips and pointers about their new backplate/wing setup.  Nothing too crazy, just first New England dive of the year with a brand new 7mm wetsuit, new backplate and wing so they just wanted help with weighting and making some minor harness adjustments; that sort of thing.

I guess she had specifically emailed and requested someone with experience using a backplate/wing since she had asked another dive shop (not in New England) and they basically had no experience with them and couldn’t really help.

I find it pretty odd nowadays that people aren’t at least familiar with them.  It’s not exactly the 90s/early 2000s where a backplate/wing was strictly considered technical gear and you might get one oddball on a boat like me with one.   A backplate/wing is nothing more than a back-inflate BCD with a simple harness.   In any case, it doesn’t take too much to adjust one properly.

She ended up pretty much having the exact same setup as me with the exception of an aluminum plate and weight pockets on her harness as opposed to weight belt.  Same wing, same plate, same single piece harness and same first stage with same hose routing. That is one good thing about backplate/wings.  The configuration is often pretty standardized.  No need to re-invent the wheel.

I later learned that another friend of mine, Dave C. actually taught her Advanced Open Water (AOW).  He prepared her well so it was really a piece of cake.

So back to the gear adjustments. I had her in a LP85 pumped to 3100psi. So more or less close to 100cu/ft of gas.  She had previously used HP80s and I believe HP100s for deeper dives. LP85s (depending on the brand) aren’t as negatively buoyant as HP100s.  They are nice tanks with a slight overfill if you don’t have HP100s available.

We tweaked the harness a little bit since the shoulder straps were a little tight in a 7mm wetsuit. I explained that you can have the shoulder straps a little less tight than you would expect. I like to be able to get a fist under the straps.  It’s really the waist strap and crotch strap that stabilize the unit; having either of those too loose can make the rig dive very unstable in my opinion.

We adjusted weighting quite a bit and of course did some weight checks on the surface. She said she was using 15lbs before but that seemed like a bit much for someone in a single-piece 7mm wetsuit (not a farmer john) her size with a steel tank and backplate.   I started her off with 14lbs but we quickly got that down to 10lbs.  For the 2nd dive I started her off with 8lbs but took the 2lb weight off the cam band for a total of 6lbs (3lbs in each weight pocket).   Not perfect but I think if we shifted weight up more to cam bands (or switching to stainless steel backplate) would actually work better for trim. Overall a success.

For both our dives max depth was around 35-38ft. We had 47f degrees on the bottom and approximately 54f degree water temperature on the surface.   Visibility was 10-15ft or so.

We saw plenty of harbor seals on the surface but all remained elusive underwater, at least for us.  Another set of divers did mention they had a brief encounter underwater.

I’ve had some pretty awesome seal encounters at Graves Light over the years but I do find the seals at Graves Light tend to be more skittish than the ones up at Dry Salvages in Gloucester or the ones at Isle of Shoals in NH.


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