Some marathon events are short enough that sleep during the race is a moot point (i.e., it would be pointless; the duration of the race is not long enough to require sleep during it). However, much like land-based marathons of this nature one does have the ability to rest and refuel (in designated areas) so long as they complete the event within the designated time limit [for the race].
While running marathons have specified distances, marathon swim distances will vary. However, the common minimum distance of a marathon swim is defined as 10K (6.21 miles) which is the distance used in the Olympic marathon swimming event and accepted by many swimming organizations.
There are a few different ways and pieces of equipment needed for your support team to get fuel/nutrients to you. The most common pieces of equipment needed for this are a telescoping (i.e., extendable) pole with some type of hook on its one end as well as some type of floating line and clips or tape (to secure food/drink containers to the line/pole). Other equipment may include a kayak, a larger boat, and/or a floating dock
Swimming helps to improve all three of the goals of cross-training- [to improve one’s] endurance, speed, and recovery leading to improvement in one’s marathon (running) performance and is considered good training for the activity.
One can swim in a rash guard in the pool or ocean, though, it may not be as comfortable as other options available on the market. While rash guards initially gained their popularity with surfers to help them avoid painful chafing (rash), from the constant contact of their body with the surfboard and the aquatic (ocean water) environment, they have since become popular for those simply swimming and/or lounging by the water- whether it’s the pool or ocean (beach)- and wanting a little added cover/protection.
Yes! You can, indeed, wear polyester in the pool. In fact, swim apparel made from a polyester blend is one of the best options to wear in the pool. A polyester blend will resist the chlorine (i.e., maintain its color longer/won’t fade as quickly; colorfast), hold its shape, resist abrasion and pilling (i.e., the fuzzball look), and have a soft and comfortable fit/feel.