you don't have to go too far offshore to get to deep waters down there do you scooby? like around here, it's a good 80 mile run to get to the canyons, which is where they do the big tuna fishing at.
not at all. someplaces as close as 10 miles offshore. depends on what you consider deep. we're looking for a lot of things but change in water pressure is one of them. you get big changes when it goes from 900ft. to 4000ft. or 2000ft to 13,000ft. you also fish current lines, follow birds, temperature changes in the water, schools of dolphin, big pile of topwater structure like huge trees or garbage piles, seamounts, etc...
i've fished a lot out in florida, carolinas, northeast. you gotta make long runs. sometimes 120 miles. if you look on google maps you can see the shelf. it actually comes closest to the u.s. just above jacksonville, north carolina. right in the outer banks area. that's where offshore fishing was invented. that's where the boats were invented. that's why they are called carolina boats. most of the original custom boat builders and sill many of the modern ones are still located there. most of the modern technology was invented there...like enclosed bridges; tuna towers, iso-props, etc... i
think at it's closest point there it's 60 miles to the shelf. but, back in the day at best you were running 15 knots. nowadays even the mid range boats will cruise out at 22-28. only the beasts run out at 33-38. in the tournaments if you need to pick up and move; for example you see something or someone else is crushing it then the big boys will run 44-46 knots. at that speed you are burning over 150 gallons an hour per side.