Diagnosis: Nothobranchius wattersi males are similar to N. kirki and differing from all other species of the genus by the following combination of characters: red colouration on caudal fin and part of caudal peduncle, anal fin red with a blue-green proximal portion, dorsal fin with light blue margin; pectoral, caudal and anal fins with black margin (Ref. 92979). It is readily distinguished from N. kirki by light blue colouration in scale centres, plain deep red colouration on caudal and distal portion of anal fin, vermiculated blue pattern on anal fin, dorsal fin blue-green, anal fin more rounded, dorsal-fin base shorter, prepelvic to preanal distance longer and head longer, with a more flattened to slightly concave shape on the upper head surface relative to N. kirki.

Description: A robust, elongate Nothobranchius species; dorsal profile slightly concave on head, convex from nape to end of dorsal-fin base; ventral profile convex, slightly concave on caudal peduncle posterior to dorsal and anal fin (Ref. 92979). Snout slightly pointed, mouth directed upwards, lower jaw longer than upper, posterior end of rictus at same level as or slightly above centre of eye (Ref. 92979). Dorsal and anal fins located posterior to mid-body; dorsal and anal fins rounded, tips with short filamentous rays; anal fin with papillate contact organs on fin rays, dorsal with few rudimentary contact organs; dorsal-fin tip not reaching caudal fin (Ref. 92979). Pectoral fin approximately triangular, tip not reaching pelvic fin; pelvic-fin tip reaching anal-fin base; caudal fin subtruncate (Ref. 92979). Scales cycloid, body and head entirely scaled, except for ventral surface of head; scales in median lateral series 26-28 + 3-4 on caudal-fin base; cephalic squamation pattern variable, some specimens presenting irregular G-type (Ref. 92979). Anterior neuromast series 'open' type (Ref. 92979).

Colouration: Males, body and head scales light blue to blue-green with dark red margin, creating a reticulated pattern on body and head; on posterior part of body and caudal peduncle scale margins wider than on anterior scales becoming completely red near caudal-fin base; operculum with three red oblique stripes; branchiostegal membrane light blue to whitish; dorsal fin blue-green with irregular red spots and dots distally denser, elongate over fin rays and smaller; complete light blue margin; anal fin red, proximally to medially with light blue to blue-green vermiculated patterns of spots and dots, with a black rim; pelvic fins light blue with red spots and with red tips; pectoral fins hyaline, light blue distally with grey to black margin; caudal fin dark red with a black narrow margin; iris golden, with faint black vertical bar through centre of eye (Ref. 92979). Females, body and head scales pale brown, with light blue iridescence on scale centres; opercular region light blue to silver; abdomen silver; all fins hyaline; iris golden, with faint black vertical bar through centre of eye (Ref. 92979).