Absolutely that speed is ridiculous if these are ocean faring vessels (especially if they’re supposed to be large navy-ish vessels)
Destroyers (even current class Arleigh Burke and future class Zumwalt) max out in the 30 knot range
Air Craft Carriers (Nimitz, and even the future Ford class) also max out in the 30 knot range
In fact the fastest “large” ships the US Navy operates are very modern (the Littoral class high-speed patrol/counter piracy ships), their design goal was 40 knots and they didn’t meet it.
For reference, 1km in 10 seconds is 100 m/s. 30 knots is 15.4~ m/s and 40 knots is 20.5~ m/s. So even if these are futuristic ships there’s absolutely nothing on the horizon that’s anywhere close to them.
edited to add: read the signature and realized this is a cold war era submarine game
by far the most popular (US) submarine class of the time was the Los Angeles class, with an official topspeed of 20 knots (although unofficial reports claim up to 33 knots in some cases), the Ohio class top speed surfaced was only 12 knots, with 20 submerged and the ‘most modern’ cold war-era class of submarines (Seawolf, there’s only 3 of them, and they were built from 89-2005, so VERY recent) is 30-35 knots (basically in the same speed as the modern destroyers and aircraft carriers.)
If you can cross 1km in 10 seconds (100 m/s) that’s 194~ knots! WAAAAY too fast, and your “absolute max time” of 15 seconds is 66 m/s which is 128~ knots, still way too fast, up to 20x faster than the submarines you’re modeling after.