[monkeyhatfork]

this is a tricky one but I'll give it a go. I grew up surfing in southern and central california so I can only speak to holdowns on waves of to about the 12ft range also a few decades younger so can't speak as to age. But as I see it the best way to be comfortable, is to get in the water as much as possible. Don't fight the hold down, you can't beat the ocean this will only drain energy, do as much stretching as possible, any breathhold excercises done on a regular basis will increase your comfort level with breatholds. But you may also want to try something without a rested recovery like apnea jogging(could walk also)-- example, start jogging, after 10-15 minutes when you have a good pace going start alternating between breaths and holding- example-- 10 sec breathing, 10 sec hold, repeat, but you can play around with those times, but keep the same pace. I grew up a block from the beach and whent out almost daily, at that time hold downs seemed almost fun and relaxing, now I live a bit inland and don't get to go out as much and always get a bit freaked out the first few till I get the hang of it again. Where are you going to surf? How Big? Reefbreak? I also find my comfort level increases quicker if I go without a leash in smaller or moderate surf so I have to chase the board around-reminds you, you can hold your own in this environment