I just wanted something that travels fast and stable on water.

Thrust:
There are 2 speeds, maneuvering speed and cruising speeds.
Maneuvering - 0-5%
Cruising - 100%

Brakes:
Activates the engine at the top, used to slow the craft down.

Pitch:
Do not pull the stick down, only push up. Activates the "spoilers", effective for slowing the craft down from 600-200ish without using the top engine.

Yaw:
It is just a redundant feature, can be used between 20-40mph.

Roll: If you find that during cruise, your ship starts to bank, this can be used to stabilize. Small movements only.

VTOL:
Push only 1 notch up or down.

Sailing with VTOL (on water) - Push slider up, tail should go beneath the water. This will be your primary rudder as well as stabilizer beneath the water.

Going on land VTOL: Push slider down, tail should rise and give you clearance to move on land. Remember to lower landing gears.

Trim:

AG3: moves the rudder under the water, use this to manipulate on water, this is your primary rudder. Always center before activating other AGs.

AG4: moves the stern thrusters to aid in faster turning. Only use this below 100mph.

AG2: This will swing your vertical stabilizer. The concept can be very odd but it works, only use this coupled with AG3. ALWAYS center the slider before activating AG2. This helps you yaw your boat without making your rudder a huge surface area to flip you over. Used best between 100-200mph.

AG1: 1 time emergency parachutes.

Concept of sailing:
You want to generally know which heading to sail before using cruise speed, as this boat requires slow speed to maneuver for stability and maintains a rigid hold when at high speed (any small movements may flip the boat or damage parts).

TL;DR:
Trim + AG 3 & 4 - slow speed maneuver (1-100mph)
Trim + AG 3 & 2 - high speed maneuver (100-200mph)
AG1 - Chutes
Cruise - AG3 only, 100% throttle.
VTOL - Rudder up or down