Does armor reduces other forms of movement speed?

[Alzrius]

A friend in another game is considering using a PC race that has a natural swim speed. A question came up as to whether wearing medium/heavy armor would reduce the character's swim speed, in addition to its land movement, and he asked me about it. I couldn't locate an answer...does armor reduce swim (and fly) speeds if it also reduces land movement?

 

[Shin Okada]

Both the entry in PHB 122 and Table 7-6 in PHB 123 says "Speed", not "Land Speed". And the description of Fly spell is mentioning about the speed when the character is wearing medium or heavy armor. "Carrying Capacity - Weight" entry in PHB P. 161 is also using the word "Speed" instead of "Land Speed". So I think both medium/heavy armor and medium/heavy load affects on all the movement mode, not just land speed.

Edit: DMG P. 20 "Armor and Encumblance" entry and it's table are also using the word Speed. Another Example is Justicator in MM 3 P.85. It's stats block shows fly speed in full plate armor (60 ft.) and base fly speed (90 ft.).