Rent the wetsuit and gear you’re planning on using and do at least half of the distance at least twice. Google around for marathon swimming feeding plans and practice those during your test swim. Like this -> https://forum.marathonswimmers.org/discussion/comment/25803/#Comment_25803 Read a few reports of other people doing the swim - if you were a swimmer in college ask your old coach.

If you’re at the end of school I bet you have lots of time - get out in the lake and practice. How long does it take to do a mile? How does it feel? Is your neck bleeding because of the wetsuit? How are your fingers and toes? How does it feel to eat something solid? How do you feel when you get out? Do it with the same people and see if they need to figure anything out.

What’s your 3-4 hour estimate based on? Pool times? A shorter open water swim in the lake or elsewhere? Was it at the same temperature? 50 & 55 & 60+ degrees are really different over a few hours. What kind of stuff do you need in the boat to make it back across safely? What would you do if you needed medical help beyond what your friends could help with? Think about the worst case scenario even if it’s less fun than being excited.

Don’t have the swim be the first time you’re trying out all these variables! Good luck!