What's too slow? 5mph is the recommended speed for deep water, per Jeep. Faster than that, and the thoughts by others here is that water gets pushed into places not designed to withstand the water pressure.
I remember being in my buddies 1987 Cherokee when he attempted to fjord a river. The ass end was so light it floated. We were literally stranded in the middle and were too light to get any traction. I think that's part of the problem with the JT. Especially with a fully inflated tire under the bed. My father-in-law had a Land cruiser with 40" inch tires and a v8. Every bit of it was steel. It wasn't floating. I think the issue isn't going in the water the issue is how long one is in there.
Whatever speed maintains a consistent bow wave is the target... it's something you just need to get a feel for in each individual vehicle but I've found a bit over 5mph to be about right. Too slow is better than too fast though... too slow might give the seals opportunity to leak but going too fast can do things like bend a fan and push it into the radiator.
I learned the speed/bow thing last week. I found 5mph kept the bow a nice smooth wave at about 25" of water, when the bow/water got a little turbulent I slowed down a smidge to get it back to being smooth
I always liked the idea of reversing through deep water to avoid intake/alternator damage. I saw a corvette do it here in Houston a few years back lol.
warm/hot metal contracts cooling will draw in water. The seals will have shorter life and start leaking... Mud,sand and grit in the water your crossing some can start failing a very short time later.... axle shaft seals... Rear main seal too. 
Somalia is pretty shitty, but the best sunrises ive seen were on the coast. Toyota took me everywhere I needed to get. Love that truck.I lived in Ethiopia for awhile. Drove these two vehicles for the NGO. God they were awesome. Really miss turning the lock on the wheel itself. Tires were usually bald but we ran tubes and somehow managed to get out of everything... Learned a lot.
(Pictures generic from internet. Ours were squared off on the front, and beat the hell up.)
How do you seal against water getting in? Any particular references on the subject? Is there any downside such as compromising the retention power of the seal or adding to heat retention?
Almost perfect, don't like how it can obstruct the view a bit, but love the below-hood install
Great piece, but the fit is super tight under the cowl and at the rear of the hood. I need to pull mine apart and trim a bit more plastic under the cowl because what they directed wasn't enough.
This is cool...but how many more inches of fjording depth do you gain from orignal OEM air intake?
