Diving conditions in the bay vary incredibly throughout the year, and one rarely knows what to expect before a dive. Cold and poor visibility are the primary complaints
- but with the deeper wrecks visibility is generally more consistent. Storms
are less of a problem in the bay than south of Cape Cod, but when the wind blows
steadily out of the north and east, the waves build quickly. Currents are generally not a problem in this area due to the protection of the Cape, and I can’t remember the last time I needed a jon line on any dive
within the bay.
Water temperature sets a definite season on the deeper wrecks by limiting run times to about 45 minutes in the dead of winter. Water temperatures in January – March generally fall in the 34 – 38 degree F range from top to bottom. Any significant deco times are VERY uncomfortable, so we generally focus on dives in the recreational range of 130 ft. or less. In late April and early May, surface temperatures begin to warm into the 40’s making some hang times possible and increasing the depth
of dives. The best season for the deeper wrecks (>180ft.) is June through October and even into the middle of November in some years. Bottom temperatures at these depths remain typically
between 44 and 48 degrees year round. A maximum run time is about 90 minutes, which
translates to a bottom time of approximately
20 - 30 minutes on the deepest wrecks (>200 FSW).
Visibility is never guaranteed and can vary from a few feet to as much as 70 ft., although this is a rare occurrence indeed. Typically “good” visibility is anything greater than 20 ft. Most deep dives are similar to
dusk or night dives – a light is required. However, some ambient light generally is available, and on rare occasions it’s possible to comfortably navigate the wrecks with the light off. If there’s a better season for visibility, it’s a close call – patterns are hard to recognize.