it is not very clear if you need to use 3 of these 6 items or 6 plus 3 more items. And this item is a sensor or a component. For example if you have a pump then if it is +1 item in your list or it must be sensor.
If it is enough to use 3 sensors from that list that you provided then make a water heater similar to Electronoobs' comment.
You then can use the waterproof thermistor (1) to measure the heated water temperature
You control heating on/off with the relay
If you attach a pump to circulate the water in the bath then you can use 1 or 2 float switches (2) (minimum and maximum water level) also a flow sensor (3) and you can display the flow speed of the circulation.
If you need 6+3 components then you can make a soda/beer can cooler.
You would circulate water around the can, and cool it with peltier element.
Depending on the thermistor you have if it is water proof or not, you can measure water in (1) and water out (+1 sensor). If you cannot measure directly the water then solder, glue, wire it to a copper pipe, then you can.
LDR (3) can be used to sense that if it is dark, you light some LEDs.
You can use the float switch (4) to control the water level.
You can use a flow sensor (5) to measure the circualation like above using a pump (6).
You can use the ultrasonic sensor (7) to switch the heating and a pump ON/OFF with the relay (
You can use DHT11 to measure enviromental conditions (9).