Almost all diving activities, whether in the tropics or in colder waters, will require some sort of exposure suit. For local conditions, this means either a full heavy wetsuit or a drysuit. For the tropics, there are thinner wetsuits and fabric skins, but these are never warm enough for use around here. Water temperatures in the north Atlantic vary from just above freezing at depth during the coldest part of the year to the mid-seventies at the surface during the warmest. Typically, you can expect high-fifties to low-sixties at depth even over the summer.
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