Safety for 48v leds in water
If you choose water-proof stripleds then you will have added about 10kV or more of electrical  insulation as most plastic is hydroscopic yet >>8kV/mm insulated. Moisture ingress to LEDs will result in rapid aging.   Most suppliers rate the waterproof types to 1m depth.

Even chlorinated water has low conductance so the water will behave as a dielectric about 80x air.  If you plan on using high slew rate PWM, keep in mind this rise in load step current and slower turn off time. But the waterproofing ought to protect you here as plastic is only about 4x air.