Structuring Long Swims in Training

What do you do (or suggest doing) for long swims in training? My weekly long swim is currently over 10,000m and 3 hours (and increasing). I don't have a regulation pool I can go to here; currently I'm doing the long swim at a hotel on the beach that has a 30m pool, and wind up doing an hour or so in the pool, an hour or so in the ocean, then the rest in the pool again. Mostly it's moderate-effort freestyle sets of the pyramid variety, every so often a length of stroke or a short (meaning up to 10min) IM set, sets like 800, 2x400, 4x200, 8x100, etc. Usually some kick and pull as well. Anything to get the distance in. Any other suggestions for structuring the long swim, or is it really just about getting the distance in however I can? Of my other swims during the week, two are interval-based (pretty much like a structured Masters workout) in the pool, one is interval-ish in the ocean (minutes of effort or strokes per minute), one is a steady ocean swim, one is an hour or so recovery swim.