You can skateboard back with the shark by throwing the shark on the ground, then going up to it and pressing E and tab at the exact same time and selecting the skateboard. Entering the pool with the shark glitched like this won't pass the mission so you need to go to the nerd spawn outside the pool in "throw a nerd in the pool" and pick up the nerd normally to get the shark back in a state where you can throw it in the pool. This strat saves about 15 seconds
the new firecracker the principal strat (which I haven't done in one of my runs yet) is after buying your items from the shop you death-warp, throw a firecracker at the ceiling in the nurse's office and it should pass the mission. This strat saves about 5 seconds.
Skipping the baseball bat saves about 16 seconds for me on my splits, 13 on getting it and the rope and 3 because the animation for punching the car is faster than the bat swing animation. The car takes 10 hits with fists and 10 hits with the bat so yeah skipping bat is fast.
My friend who found shark glitch was doing some stuff with "rocket jumping" although his strat was taking the lighter and lighting the car that spawns in front of the school on fire and launching out of that, he consistently got in the water for shark but with the ragdoll it ended up being slower, since he went further away from the shark than when we take the fire truck to it.
Also I forgot to mention, the shark glitch also works on any object you interact with such as nerds (which isn't particularly useful in the run but still neat) and the gurney.
Additionally minor optimization, after firecracker principal do the gurney glitch and go talk to the bullies with the gurney glitch then go straight to the lake, saves about 10 seconds.
Great thoughts. Going to try it with my friend