I've on occasion been interested in doing some underwater shooting (mostly swimming pool/ snorkel level of shooting though - for triathlons and swim training in particular)
Any advice on an affordable (even via rental) way to get in to this, for occasional use ?
I've seen what sort of look like ziploc bags with lens openings (maybe slightly heavier plastic

) all the way up to the full 'work every button through' cases for my camera that costs about $5k.
Anyone care to list out the entry options into underwater shooting (again, not diving so much) ? Is there a middle ground between using a plastic bag and using the full housings ?